Optical scanner

ABSTRACT

An optical scanner comprises a support member for fixation on a given member, a movable plate provided with a reflection surface for reflecting light, an elastic member coupling the movable plate and the support member, the elastic member comprising a plurality of laminated organic elastic insulating layers, an actuator, provided at least on the movable plate, for producing a driving force between the movable plate and the support member, and an electric element for applying a predetermined electric signal to the actuator and thus producing the driving force, thereby elastically deforming the elastic member and deflecting the movable plate. The electric element is provided between the organic elastic insulating layers of the elastic member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Continuation-in-Part application of U.S. patent applicationSer. No. 08/840,596, filed Apr. 22, 1997, the entire contents of whichare incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to an optical scanner which reflects lightfrom a light source and scans the reflected light.

<First Prior Art>

As a conventional optical scanner, Jpn. Pat. Appln. KOKAI PublicationNo. 63-82165 discloses an optical scanner having an arrangement like theone shown in FIGS. 45A and 45B, i.e., a deflector 300.

As shown in FIG. 45B, the deflector 300 includes a large york 328, acoil 329 wound around the york 328, and an optical deflecting element310 placed in the space inside the york 328.

As shown in FIG. 45A, the optical deflecting element 310 includes amirror 312, a driving coil 311, and ligaments 313 and 314. Thesecomponents are integrally formed and supported by a support frame 315.

In the deflector 300, the ligaments 313 and 314 are twisted by the forceexerted on the driving coil 311 owing to the interaction between acurrent flowing in the driving coil 311 and a magnetic field generatedby the york 328 and the coil 329. As a result, the mirror 312 isvibrated at a predetermined frequency.

Light is irradiated on the mirror 312, and the reflected light isscanned one-dimensionally.

<Second Prior Art>

As another conventional optical scanner, Jpn. Pat. Appln. KOKAIPublication No. 6-46207 discloses an optical scanner designed to vibrateits reflecting surface by using a piezoelectric element.

As shown in FIG. 46, in this optical scanner, a cantilever constitutedby a carrier material 2 and an electrode 3 is supported on a siliconsubstrate 1.

This cantilever constitutes a unimorph piezoelectric actuator 6. Theunimorph piezoelectric actuator 6 is manufactured by sequentiallyforming the carrier material 2 and the electrode 3 on the upper surfaceof the silicon substrate 1, and forming a space 7 by etching.

A strain gage 9 is placed on the cantilever. Another strain gage 10 isplaced at the fixed end of the cantilever.

The strain gage 9 is used to measure the deformation amount of theunimorph piezoelectric actuator 6. The strain gage 10 is used to obtaina reference signal for the measuring operation.

According to this optical scanner, the deformation-free distal endportion of the cantilever functions as a reflecting surface, on whichlight is irradiated.

The cantilever is vibrated by the unimorph piezoelectric actuator 6. Asa result, light reflected by the distal end portion of the cantilever isscanned one-dimensionally.

The optical scanner as the first prior art disclosed in Jpn. Pat. Appln.KOKAI Publication No. 63-82165 requires the large york 328 and the coil329 to obtain a sufficient driving force. The overall structure of thisdevice is large.

Recently, demands have arisen for compact optical scanners. However, asthe overall size of a scanner is reduced to meet such demands, thedriving force is reduced, and hence the deflection angle of a scan beambecomes insufficient. In addition, this scanner requires a cumbersomemechanical assembly process.

The optical scanner as the second prior art disclosed in Jpn. Pat.Appln. KOKAI Publication No. 6-46207 is smaller in size than the aboveoptical scanner. However, the deflection angle of a scan beam is notlarge enough to meet the future demands.

In addition, as the electric elements of this optical scanner, e.g., theelectrode 3 and the electrodes of the strain gages 9 and 10 are exposed,no countermeasures are taken against aging. That is, a problem is posedin terms of maintenance of stable performance.

<Third Prior Art>

Still another known compact optical scanner includes a vibration inputportion formed by bonding a scan portion for reflecting light, anelongated elastic deformation portion, and a piezoelectric actuator. Thereflecting portion is vibrated two-dimensionally by the piezoelectricactuator to scan light.

Such an optical scanner is disclosed, for example, in Jpn. Pat. Appln.KOKAI Publication No. 5-100175.

FIGS. 47A and 47B show the structure of a silicon substrate 1 disclosedin Jpn. Pat. Appln. KOKAI Publication No. 5-100175.

This optical scanner 1 comprises a thin plate 6 and a piezoelectricactuator 21.

On the plate 6, a vibration input portion 5, an elastic deformationportion 2, a scan portion 3, and a weight portion 3W are integrallyformed.

The piezoelectric actuator 21 is formed by bonding a strain conversionelement 23 to a multilayered piezoelectric element 22.

The scan portion 3 has a mirror surface 4 for reflecting a light beam.

In the optical scanner 1 having the above structure, when a voltage isapplied to the piezoelectric actuator 21 bonded to the vibration inputportion 5 to vibrate the vibration input portion 5, the elasticdeformation portion 2 resonates, and the scan portion 3 pivots about anaxial center P in FIG. 47A within the range of an angle θ_(T). At thesame time, the scan portion 3 pivots about an axial center Q in FIG. 47Bwithin the range of an angle θ_(B).

In this case, the piezoelectric actuator 21 vibrates the vibration inputportion 5 in a vibration mode in which vibrations having a resonantfrequency of a torsional deformation mode are superimposed on vibrationshaving a resonant frequency of a bending deformation mode. As a result,the torsional deformation mode and the bending deformation mode areamplified by the elastic deformation portion 2, and the torsionalvibrations and the bending vibrations are synthesized at the scanportion 3.

In the optical scanner 1 having the above structure, two-dimensionaloptical scanning is realized by controlling the voltage applied to thepiezoelectric actuator 21 using a driving circuit (not shown).

<Fourth Prior Art>

Still another known compact optical scanner uses a silicon semiconductorsubstrate and a helical torsion spring. This optical scanner uses anoptical deflecting element for scanning light by swinging a reflectorusing an electromagnetic force.

Such an optical scanner is disclosed, for example, in “TECHNICAL DIGESTOF THE SENSOR SYMPOSIUM”, 1995, pp. 17-20.

FIGS. 48A and 48B show the structure of the optical scanner disclosed inthis reference.

This optical scanner has a reflector 34 and helical torsion springs 33,formed on a silicon semiconductor substrate 31, together with a fixingframe 50 for supporting them. These components are integrated into anoptical deflecting element.

Flat coils 35 are arranged around the peripheral portion of thereflector 34. The flat coils 35 are electrically connected to electrodes36 on the fixing frame 50 through the helical torsion springs 33.

In addition, circular permanent magnets 38 are located through a spacerinsulating substrate 40 such that the direction of magnetization of eachpermanent magnet 38 is parallel to the reflector 34 and makes an angleof about 45° with the axial direction of the helical torsion spring 33.

When an AC current is applied to the flat coil 35, a Lorentz force isgenerated therein owing to the interaction between the current and themagnetic field generated by the permanent magnet 38.

This Lorentz force causes the reflector 34 to swing in the twistingdirection of the helical torsion spring 33.

When a current having the same frequency as the resonant frequencydefined by the elastic properties of the helical torsion spring 33 andthe mass and center of gravity of the reflector 34 is applied to theflat coil 35, the maximum amplitude at the current value can beobtained.

In this case, the reflector 34 is vacuum-sealed to reduce the dampingcoefficient.

Referring to FIGS. 48A and 48B, reference numeral 39 denotes a gasabsorbent; 41, a front cover insulating substrate; 42, a lower surfaceinsulating substrate and 32, a movable plate.

In the third and fourth prior-art techniques, there is no descriptionconcerning the durability of electric elements such as wiring layers forthe optical scanner which vibrates at large deflection angles. Moreover,in the third prior art, there is no description concerning theprotection of the electric elements against the atmosphere.

<Fifth Prior Art>

As a conventional optical scanner, there is also known a lightdeflecting element disclosed, for example, Jpn. Pat. Appln. KOKOKUPublication No. 60-57052. In this light deflecting element, as shown inFIG. 73, a spring portion 1002 and a movable portion 1003 supported bythe spring portion 1002 are formed of a single insulating substrate1001. The movable portion 1003 is provided with a reflection mirror 1004and a coil pattern 1005. The spring portion 1002, movable portion 1003,reflection mirror 1004 and coil pattern 1005 are formed byphotolithography and etching technique. According to this lightdeflecting element, the spring portion 1002 is torsion-vibrated andthereby reflected light can be scanned in a predetermined direction.

In this conventional optical scanner, wiring for supplying current tothe coil pattern 1005 is formed on a surface of the spring portion 1002or an elastic member. The reason is that in the conventional opticalscanner, like the light deflecting element described in Jpn. Pat. Appln.KOKOKU Publication No. 60-57052, the spring portion 1002 is formed ofsingle insulating substrate 1001 and thus there is no choice but toprovide wiring on the surface of the spring portion 1002. In thestructure wherein wiring is formed on the surface of spring portion1002, however, there arises such a problem that when the spring portion1002 is bent or torsion-vibrated, the wiring is adversely affected by agreat stress occurring at the surface of the spring portion 1002. Ingeneral, optical scanners are so controlled that they may bereciprocally moved over and over. If a great stress acts on the wiringrepeatedly, the wiring will degrade and, in a worst case, such fault asbreakage of wiring will occur.

BRIEF SUMMARY OF THE INVENTION

The first object of the present invention is to provide an opticalscanner which can set the deflection angle of a scan beam to a largeangle.

It is the second object of the present invention to provide an opticalscanner which has the above advantage and allows electric elements tohave high durability.

It is the third object of the present invention to provide an opticalscanner which has the above advantages and allows mass production at alow cost.

It is the fourth object of the present invention to provide an opticalscanner which has the above advantages and further includes deflectionangle detection means.

In order to achieve the above objects, according to the presentinvention, there is provided an optical scanner comprising a supportmember for fixing the scanner to a given member, a movable plate with amirror surface for reflecting light, an elastic member formed of aplurality of organic elastic insulating layers for connecting thesupport member and the movable plate, an actuator, provided at least onthe movable plate, for producing a driving force between the movableplate and the support member, and an electric element for applying apredetermined electric signal to the actuator, thereby producing thedriving force, the electric element being provided between the organicinsulating layers of the elastic member.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention, and together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIG. 1 is a perspective view showing the structure of an optical scanneraccording to the first embodiment of the present invention;

FIG. 2 is an exploded perspective view showing a structure as part ofthe optical scanner in FIG. 1;

FIG. 3 is a partially sectional perspective view showing the opticalscanner in FIG. 1;

FIG. 4 is a view showing an applied example of the optical scanneraccording to the first embodiment;

FIG. 5 is an exploded perspective view showing a structure as amodification of the optical scanner according to the first embodiment ofthe present invention;

FIG. 6 is a perspective view showing the structure of anothermodification of the optical scanner according to the first embodiment ofthe present invention;

FIG. 7 is a sectional view showing the structure of an optical scanneraccording to the second embodiment of the present invention;

FIGS. 8A to 8I are sectional views for explaining the manufacturingprocess for the structure of the optical scanner in FIG. 7;

FIG. 9 is a perspective view showing a structure as a modification of anoptical scanner according to the second embodiment of the presentinvention;

FIG. 10 is a perspective view showing the structure of an opticalscanner according to the third embodiment of the present invention;

FIG. 11 is a sectional view taken along a line XI—XI of the opticalscanner in FIG. 10;

FIGS. 12A to 12J are sectional views for explaining the manufacturingprocess for the structure of the optical scanner in FIGS. 10 and 11;

FIG. 13 is a perspective view showing a structure as a modification ofan optical scanner according to the third embodiment of the presentinvention;

FIG. 14 is a perspective view showing the structure of anothermodification of the optical scanner according to the third embodiment ofthe present invention;

FIG. 15 is a top view showing the dimensions of a structure used in anexperiment;

FIG. 16 is a sectional view taken along a line XVI—XVI of the structurein FIG. 15;

FIG. 17 is a graph showing the relationship between the current flowingin a flat coil and the deflection angle of an optical scanner;

FIG. 18 is a graph showing the relationship between the current flowingin the flat coil and the electric resistance of the flat coil while amovable plate is not vibrated;

FIG. 19 is a top view showing the structure of an optical scanneraccording to the fourth embodiment of present invention;

FIG. 20 is a sectional view taken along a line XX—XX of the structure ofthe optical scanner in FIG. 19;

FIG. 21 is a block diagram showing a driving circuit for the opticalscanner using the structure in FIG. 19;

FIG. 22 is a perspective view showing the structure of an opticalscanner according to the fifth embodiment of the present invention;

FIGS. 23A and 23B are a plan view and a sectional view, respectively,showing the structure of a driving coil in the fifth embodiment of thepresent invention;

FIGS. 24A to 24E are sectional views showing the manufacturing processfor an optical scanner according to the fifth embodiment of the presentinvention;

FIGS. 25A to 25D are sectional views showing the manufacturing processfor the optical scanner according to the fifth embodiment of the presentinvention;

FIG. 26 is a view showing an application example of the optical scanneraccording to the fifth embodiment of the present invention;

FIG. 27 is a perspective view showing the structure of a modification ofthe optical scanner according to the fifth embodiment of the presentinvention;

FIG. 28 is a perspective view showing the structure of an opticalscanner according to the sixth embodiment of the present invention;

FIG. 29 is a perspective view showing the structure of the firstmodification of the optical scanner according to the sixth embodiment ofthe present invention;

FIGS. 30A and 30B are plan views respectively showing the structures ofdriving coils in modifications of the fifth and sixth embodiments of thepresent invention;

FIG. 31 is a perspective view showing the structure of the secondmodification of the optical scanner according to the sixth embodiment ofthe present invention;

FIGS. 32A and 32B are plan views respectively showing the structures ofdriving coils in the first and second modifications of the sixthembodiment of the present invention;

FIG. 33 is a sectional view showing the structure of an optical scanneraccording to the seventh embodiment of the present invention;

FIG. 34 is a plan view showing the structure of the optical scanneraccording to the seventh embodiment of the present invention;

FIG. 35 is a view showing an application example of the optical scanneraccording to the seventh embodiment of the present invention;

FIG. 36 is a perspective view showing the structure of an opticalscanner according to the eighth embodiment of the present invention;

FIG. 37 is a sectional view taken along a line 37-37′ in the eighthembodiment shown in FIG. 36;

FIG. 38 is a sectional view taken along a line 38-38′ in the eighthembodiment shown in FIG. 36;

FIG. 39 is a plan view showing the structure of a driving coil in theeighth embodiment of the present invention;

FIGS. 40A to 40J are sectional views showing the manufacturing processfor the optical scanner according to the eighth embodiment of thepresent invention;

FIG. 41 is a perspective view showing an application example of theoptical scanner according to the eighth embodiment of the presentinvention;

FIG. 42 is a perspective view showing the structure of a modification ofthe optical scanner according to the eighth embodiment of the presentinvention;

FIG. 43 is a sectional view taken along a line 43-43′ in themodification of the eighth embodiment of the present invention in FIG.42;

FIG. 44 is a sectional view taken along a line 44-44′ in themodification of the eighth embodiment of the present invention in FIG.42;

FIGS. 45A and 45B are views showing the structure of an optical scanneraccording to the first prior art;

FIG. 46 is a sectional view showing the structure of an optical scanneraccording to the second prior art;

FIGS. 47A and 47B are perspective views showing the structure of anoptical scanner according to the third prior art;

FIGS. 48A and 48B are views showing the structure of an optical scanneraccording to the fourth prior art;

FIG. 49 is a perspective view showing the structure of an opticalscanner according to a ninth embodiment of the invention;

FIG. 50 is a sectional view taken along a line A—A or a central axis ofthe optical scanner in FIG. 49;

FIG. 51 is a sectional view taken along a line B—B of the opticalscanner in FIG. 49;

FIGS. 52A to 52I are views showing the manufacturing process for theoptical scanner according to the ninth embodiment;

FIG. 53 is a view showing the state of use of the optical scanneraccording to the ninth embodiment;

FIG. 54 is a perspective view showing a modification of the opticalscanner according to the ninth embodiment;

FIG. 55 is a perspective view showing a modification of the opticalscanner according to the ninth embodiment;

FIG. 56 is a perspective view showing a modification of the opticalscanner according to the ninth embodiment;

FIG. 57 is a perspective view showing the structure of an opticalscanner according to a tenth embodiment of the invention;

FIG. 58 is a sectional view taken along a line A—A of the opticalscanner in FIG. 57;

FIG. 59 is a sectional view taken along a line B—B of the opticalscanner in FIG. 57;

FIG. 60 is a plan view showing a movable plate and an elastic member ofthe optical scanner according to the tenth embodiment;

FIGS. 61A to 61J are views showing the manufacturing process for theoptical scanner according to the tenth embodiment;

FIG. 62 shows a simulation result of a stress acting on the wiring ofthe optical scanner according to the tenth embodiment;

FIG. 63 shows a simulation result of a stress acting on the wiring ofthe optical scanner according to the tenth embodiment;

FIG. 64 shows a simulation result of a stress acting on the wiring ofthe optical scanner according to the tenth embodiment;

FIG. 65 shows a simulation result of a stress acting on the wiring ofthe optical scanner according to the tenth embodiment;

FIG. 66 shows an example of the optical scanner of the tenth embodiment,which is applied to a laser scanning microscope;

FIG. 67 is a perspective view showing a modification of the opticalscanner according to the tenth embodiment;

FIG. 68 is a perspective view showing a modification of the opticalscanner according to the tenth embodiment;

FIG. 69 is a plan view showing an elastic member of an optical scanneraccording to an eleventh embodiment of the invention;

FIG. 70 is a sectional view taken along a line A—A of the opticalscanner in FIG. 69;

FIG. 71 is a block diagram showing a control circuit of the opticalscanner according to the eleventh embodiment;

FIGS. 72A to 72J are views showing the manufacturing process for theoptical scanner according to the eleventh embodiment; and

FIG. 73 is a perspective view showing a conventional optical scanner.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the presently preferredembodiments of the invention as illustrated in the accompanyingdrawings, in which like reference characters designate like orcorresponding parts throughout the several drawings.

Optical scanner devices according to the embodiments of the presentinvention will be described below with reference to the accompanyingdrawings.

(First Embodiment)

An optical scanner according to the first embodiment of the presentinvention will be described with reference to FIGS. 1 to 4.

As shown in FIGS. 1 and 3, the optical scanner includes a structure 100whose free end is vibrated, and a permanent magnet 108 placed near thefree end of the structure 100.

As shown in FIGS. 1 to 3, the structure 100 includes a support member104 serving as a support portion which is a fixed end, a flexiblesubstrate 101 which is an elastically deformable elastic portion, and amovable plate 105 having a reflecting surface serving as a mirror.

The support member 104 and the movable plate 105 are fixed to the twoend portions of the flexible substrate 101 by bonding.

In this case, the flexible substrate is a thin plate member consistingof an organic insulating material.

In order to obtain high linearity in the scanning direction of light(i.e., in order to make the path of a scan light beam reciprocate on thesame straight line without shifting), the support member 104 and themovable plate 105 are bonded to the flexible substrate 101 such that thecentral axis of the movable plate 105 coincides with that of the supportmember 104.

In this case, the direction in which the structure 100 extends from thesupport member 104 to the movable plate 105 is defined as thelongitudinal direction, and a direction perpendicular thereto is definedas the widthwise direction.

In the following embodiment, the longitudinal and widthwise directionsare defined in the same manner.

The flexible substrate 101, the support member 104, and the movableplate 105 have the same width. The above bonding can be easily realizedby bonding the movable plate 105 and the support member 104 as the twoends of each member in the widthwise direction are aligned with the twoends of the flexible substrate 101 in the widthwise direction.

The flexible substrate 101 incorporates a flat coil 102 surrounding theinside of the periphery of the flexible substrate 101. The two endportions of the flat coil 102 are connected to electrode pads 103. Theelectrode pads 103 are exposed on the upper surface of the flexiblesubstrate 101 so that the flat coil 102 can be electrically connected toexternal parts.

The movable plate 105 has a reflecting surface on the opposite side tothe surface bonded to the flexible substrate 101.

The material to be used for the movable plate 105 is determined by theperformance of an optical scanner.

If, for example, scanning is to be performed at a low frequency, themass of the movable plate 105 is preferably large. A high-densitymaterial such as a metal is therefore suited for the movable plate 105.

In contrast to this, if scanning is to be performed at a high frequency,the mass of the movable plate 105 is preferably small. A low-densitymaterial such as plastic is therefore suited for the movable plate 105.

If the movable plate 105 consists of a plastic material, the reflectingsurface of the movable plate 105 is obtained by forming a filmconsisting of a material having a high reflectance such as a metal byelectroless plating.

The support member 104 is used to fix the structure 100 with a die castor the like, and hence preferably consists of a thick plate having ahigh strength such as a metal plate, e.g., a thick plate consisting ofstainless steel.

If the support member 104 is not firmly fixed to the structure 100 witha die cast, the operation of the optical scanner is adversely affected.For this reason, the support member 104 is preferably bonded to thestructure 100 firmly with a die cast.

The portion between the support member 104 and the movable plate 105 onthe flexible substrate 101 serves as an elastic portion, i.e., a leafspring portion 106, which supports the movable plate 105 to make itdisplaceable with respect to the support member 104.

The flexible substrate 101 has a through hole 107 in the middle of theleaf spring portion 106, i.e., the inside of the flat coil 102.

The through hole 107 helps the displacement of the movable plate 105.

In order to realize a one-dimensional scanning operation with highlinearity, the center of the through hole 107 is preferably located inthe middle of the leaf spring portion 106 in the widthwise direction,and the through hole 107 preferably has a shape symmetrical about acentral axis perpendicular to the widthwise direction.

In addition, the through hole 107 is preferably shaped to prevent stressfrom concentrating on a specific portion upon displacement of themovable plate 105.

For the above reasons, the through hole 107 preferably has a circularshape, an elliptic shape, or a polygonal shape with round corners.

The permanent magnet 108 is positioned such that its direction ofmagnetization is almost parallel to the vibrating direction of themovable plate 105, and the distal end of the permanent magnet upperportion is set at an arbitrary position at about 45° in the upward ordownward direction with respect to the flat coil 102 located at thedistal end portion of the movable plate 105.

The operation of the optical scanner having the above structure will bedescribed next.

Alternating currents are supplied from a power supply (not shown) to theflat coil 102 through the electrode pads 103.

When a current flows in the flat coil 102, a portion of the flat coil102 near the free end of the structure 100, i.e., a portion of the flatcoil 102 which extends parallel to the side of the free end of thestructure 100, mainly receives a force generated by the interactionbetween the current and the magnetic field generated by the permanentmagnet 108.

Since the current flowing in the flat coil 102 is an alternatingcurrent, the direction of the force exerted on the above portion of theflat coil 102 periodically changes.

The movable plate 105 therefore vibrates in the direction of thickness.

The resonant frequency of the vibration of the structure 100 is uniquelydetermined by the shapes and materials of the movable plate 105 and theleaf spring portion 106. When the alternating current supplied to theflat coil 102 has the same frequency as the resonant frequency, thevibration of the movable plate 105 has the maximum amplitude.

This resonant frequency, the gain at the time of resonance, and thedeflection angle of the movable plate 105 are approximately given byequations (1), (2), and (3) below. These equations are used as modelsfor actual design.

When light from a light source is reflected by the movable plate 105 tobe scanner, the deflection angle of the light is twice the deflectionangle of the movable plate 105.

fr={6Ep Ipπla ³/(mass+0.23 mcp)}^(½)  (1)

gain=1/[{1.0−(f/fr)²}²+(2.0 dp·f ² /fr)]^(½)  (2)

i _(max) =gain*w[(lb ²/2Es Is)+{(la+lb)² −lb2}/2Ep Ip]  (3)

where fr is the resonant frequency, Ep is the Young's modulus of theleaf spring portion 106, Ip is the second moment of area of the leafspring portion 106, mass is the mass of the movable plate 105, mcp isthe mass of the leaf spring portion 106, gain is the gain at the time ofresonance, I is an arbitrary frequency, dp is the damping coefficient,i_(max) is the deflection angle at the time of resonance, w is themomentum generated in the flat coil 102, Es is the Young's modulus ofthe movable plate 105, Is is the second moment of area of the movableplate 105, lb is the length of the leaf spring portion 106, and la isthe length of the movable plate 105.

The optical scanner according to this embodiment is used in a state, forexample, as shown in FIG. 4. If a collimated laser beam from a laserlight source 109 is radiated on the reflection surface of the vibratingmovable plate 105, a laser beam 108 reflected by the reflection surfaceof the movable plate 105 is scanned one-dimensionally. As a result, ascan line 110 is obtained. If a predetermined current is applied to theflat coil 102 (see FIG. 1) as a drive signal at a predeterminedfrequency, scanning can be performed at desired frequency and amplitude.Optical characteristics obtained along the scan line 110 are detected bya light-receiving element 111, and a detection signal is output to asignal processing circuit 112. The signal processing circuit 112 readsthe optical characteristics on the scan 110. Since this scanner can beremarkably reduced in size, compared to the conventional scanner, it issuitably applied to small-sized devices and the power consumption can bereduced.

In this embodiment, the flat coil 102 surrounds the periphery of theflexible substrate 101 within the range from the movable plate 105 tothe support member 104.

Since the portion influenced by the magnetic flux generated by thepermanent magnet 108 is substantially only a portion of the flat coil102 which is formed parallel to the end portion of the movable plate105, the vibration is stabile, and modes other than the longitudinalvibration mode hardly occur.

In addition, since wiring layers other than the flat coil 102 are notrequired, this optical scanner can be easily manufactured, thusrealizing high productivity.

Furthermore, in this optical scanner, electric elements such as wiringlayers are integrally formed on the flexible substrate 101. For thisreason, the flat coil 102 and the like need not be handled as discretecomponents.

Since the flat coil 102 used in this case, in particular, consists of athin film to realize a compact optical scanner, the flat coil 102 isdifficult to handle. For this reason, the flat coil 102 is formed in theflexible substrate 101 to be handled together with the flat coil 102,thereby greatly improving the productivity.

This optical scanner requires only a small number of assembly steps, andcan be completed by only bonding the support member 104 and the movableplate 105 to the flexible substrate 101.

Since this optical scanner requires only a small number of assemblysteps, the optical scanner is almost free from unstable vibrations dueto problems in terms of assembly.

The direction of the scanner in use is not fixed, and the scanner mustbe so designed as to be used in any direction. The problem in this caseis that the vibrating portion of the optical scanner is twisteddepending on the direction of the optical scanner. In this embodiment,an analysis of this problem has led to the finding that the formation ofthe through-hole 107 in the middle of the leaf spring portion 106 canrealize a structure which is resistant to the twist and provides a largedeflection angle. With the provision of the through-hole 107, thestrength characteristics of the leaf spring portion 106 are improved.

Note that since stress concentrates on the four corners of the throughhole 107, the four corners have curvatures to disperse the stress aroundthe corners.

By using the flexible substrate 101 mainly consisting of an organicmaterial for the leaf spring portion 106, the leaf spring portion 106 isresistant to brittle fracture and attains a large deflection angle whilemaintaining the minimum necessary strength.

In addition, since the flat coil 102 is formed in the flexible substrate101, the flat coil 102 is almost free from aging due to humidity.

Furthermore, the flexible substrate 101 serves to insulate the wiringlayers of the flat coil 102 from each other.

As is apparent, each arrangement of this embodiment can be variouslymodified and changed.

FIG. 5 shows a modification of this embodiment.

As shown in FIG. 5, the flat coil 102 surrounds the area in which themovable plate 105 is bonded, and the end portions of the flat coil 102are electrically connected to the electrode pads 103, which are arrangedon the portion to which the support member 104 is bonded, through wiringlayers 113.

Although the wiring layer 113 connected to the end portion of the flatcoil 102 which is located on the front side in FIG. 5 extends over theflat coil 102, this portion is properly insulated by the organic film ofthe flexible substrate 101.

The flexible substrate 101 therefore has a multilayered structureconsisting of the flat coil 102, the insulating organic film, the wiringlayers 113, the electrode pads 103, and the organic films sandwichingthese components.

The strength of a leaf spring portion 106 having wiring layers extendingtherein can be controlled more easily than a leaf spring portion 106having a flat coil extending therein. In addition, since the overallresistance of the flat coil 102 can be reduced, the power consumed bythe optical scanner can be reduced.

FIG. 6 shows another modification of this embodiment.

As shown in FIG. 6, the support member 104 surrounds the movable plate105, and the permanent magnet 108 is fixed to the support member 104.

The portion of the support member 104 to which the permanent magnet 108is fixed is cut by about 20 μm by etching or the like. The bondingsurface of the permanent magnet 108 is coated with an adhesive or thelike and bonded to the etched portion.

In this structure, since the mounting position of the permanent magnet108 is specified by etching, the permanent magnet 108 can always bemounted at the same position. In addition, the permanent magnet 108 canbe easily mounted within a short period of time.

<Second Embodiment>

FIGS. 7 and 8A to 8I show an optical scanner according to the secondembodiment of the present invention.

The outer appearance of a structure 200 of this embodiment in FIG. 7 isthe same as that of the structure 100 of the first embodiment in FIGS. 1to 3. However, the structure 200 of this embodiment differs from thestructure 100 in that the former is integrally manufactured by asemiconductor manufacturing technique.

Referring to FIG. 7, a support member 201 and a movable plate 202 areformed from a single substrate.

In this case, a single-crystal silicon substrate having a (100) plane isused for this substrate. Silicon nitride films 203 are formed on thesilicon substrate.

A first polyimide layer 204 is formed on the silicon nitride film 203. Aflat coil 205 is formed on the first polyimide layer 204.

In forming the flat coil 205, an aluminum film is formed by sputteringand processed into a coil pattern by etching.

The flat coil 205 surrounds a portion near the periphery of thestructure 200. The two ends of the flat coil 205 are connected toelectrode pads 206 which are used for electric connection to externalparts.

The underlayer of the electrode pad 206 is formed together with the flatcoil 205. Thereafter, aluminum is deposited on the underlayer bysputtering to increase the thickness of the layer.

A second polyimide layer 207 is formed on the flat coil 205.

The second polyimide layer 207 is part of a leaf spring portion 208 andserves as an insulating film between the coil wiring layers of the flatcoil 205. The second polyimide layer 207 also serves to reduce the leveldifferences produced by the flat coil 205.

A third polyimide layer 209 is formed on the second polyimide layer 207.

The first polyimide layer 204, the second polyimide layer 207, and thethird polyimide layer 209 constitute the leaf spring portion 208 whichsupports the movable plate 202 to make it displaceable with respect tothe support member 201.

The third polyimide layer 209 is formed, in particular, to match thespring property of the leaf spring portion 208 with the design value.

The second polyimide layer 207 and the third polyimide layer 209 are notformed on the electrode pads 206. That is, the electrode pads 206 areexposed and can be electrically connected to external parts.

Note that if the desired spring property of the leaf spring portion 208can be obtained by the first and second polyimide layers, the thirdpolyimide layer need not be formed.

A through hole 210 is formed in the leaf spring portion 208.

In order to realize a one-dimensional scanning operation with highlinearity, the center of the through hole 210 is preferably located inthe middle of the leaf spring portion 208 in the widthwise direction,and the through hole 107 preferably has a shape symmetrical about acentral axis perpendicular to the widthwise direction.

In addition, the through hole 208 is preferably shaped to prevent stressfrom concentrating on a specific portion upon displacement of themovable plate 105.

For the above reasons, the through hole 210 preferably has a circularshape, an elliptic shape, or a polygonal shape with round corners.

A permanent magnet 211 is positioned such that its direction ofmagnetization is nearly parallel to the vibrating direction of themovable plate 202, and the distal end of the permanent magnet upperportion is set at an arbitrary position at about 45° in the upward ordownward direction with respect to the flat coil 205 located at thedistal end portion of the movable plate 202.

A method of manufacturing the structure 200 of the optical scanner ofthis embodiment will be described next with reference to FIGS. 8A to 8I.

As shown in FIG. 8A, a silicon substrate 212 is cleaned, and siliconnitride films 203 are formed on the surfaces of the silicon substrate212 by using a low-pressure CVD apparatus.

The silicon nitride film 203 on the upper surface servers as aninsulating layer between a flat coil 205 to be formed on the siliconnitride film 203, and the silicon substrate 212. The silicon nitridefilm 203 on the lower surface is used as a mask material when a movableplate 202 to be formed later is isolated from the support member 201.

As shown in FIG. 8B, for the above reason, the silicon nitride film 203on the lower surface is patterned such that the silicon on the portionto be removed by dry etching is exposed.

A mask 213 used to form a through hole 210 in a leaf spring portion 208is formed on the silicon nitride film 203 on the upper surface by usingan aluminum film formed by sputtering.

As shown in FIG. 8C, a first polyimide layer 204 is formed on thesilicon nitride film 203 on the upper surface.

The first polyimide layer is formed by coating the silicon nitride film203 with a polyimide solution, uniformly forming a polyimide film byprinting or spin coating, and sintering the film.

As shown in FIG. 8D, a flat coil 205 is formed on the first polyimidelayer 204.

The flat coil 205 is formed by etching a sputtered aluminum film into acoil pattern.

Thereafter, an aluminum film is formed on only the portion correspondingto an electrode pad 206 by sputtering again to form an electrode pad 206having a sufficient thickness.

As shown in FIG. 8E, a second polyimide layer 207 is formed on the firstpolyimide layer 204. Similar to the first polyimide layer 204, thesecond polyimide layer 207 is formed by coating the first polyimidelayer 204 with a polyimide solution, uniformly forming a polyimide filmby printing or spin coating, and sintering the film.

As shown in FIG. 8F, a third polyimide layer 209 is formed on the secondpolyimide layer 207.

In this case, the third polyimide layer 209 is formed to be thicker thanthe first polyimide layer 204 and the second polyimide layer 207 toincrease the rigidity of a leaf spring portion 208 to be formedafterward.

Similar to the first polyimide layer 204, the third polyimide layer 209is formed by coating the second polyimide layer 207 with a polyimidesolution, uniformly forming a polyimide film by printing or spincoating, and sintering the film.

As shown in FIG. 8G, the portions of the second and third polyimidelayers 207 and 209 which are located above a through hole 210 and theelectrode pad 206 are selectively removed by dry etching.

As shown in FIG. 8H, the silicon substrate 212 is anisotropically etchedfrom its lower surface side by using an alkaline solution and thepatterned silicon nitride film 203 on the lower surface as a mask,thereby forming a movable plate 202 and a support member 201.

In this case, the silicon nitride film 203 under the first polyimidelayer 204 serves as a masking layer for protecting the first polyimidelayer 204 from this anisotropic etching.

As shown in FIG. 8I, the silicon nitride film 203 serving as the maskinglayer for the first polyimide layer 204 is removed by dry etching afterthe silicon is etched.

When the silicon nitride film 203 is removed, the mask 213 used to etchthe first polyimide layer 204 appears under the leaf spring portion 208.

The first polyimide layer 204 is processed by using this mask 213 toform a through hole 210.

Finally, the mask 213 is removed by etching to obtain the structure 200of the optical scanner of this embodiment described above.

The operation of the optical scanner of this embodiment will bedescribed next.

Alternating currents are supplied from a power supply (not shown) to theflat coil 205 through the electrode pads 206.

When a current flows in the flat coil 205, a portion of the flat coil205 near the free end of the structure 200, i.e., a portion of the flatcoil 205 which extends parallel to the side of the free end of thestructure 200, mainly receives a force generated by the interactionbetween the current and the magnetic field generated by the permanentmagnet 211.

Since the current flowing in the flat coil 205 is an alternatingcurrent, the direction of the force exerted on the above portion of theflat coil 205 periodically changes.

The movable plate 202 therefore vibrates in the direction of thickness.

The resonant frequency of the vibration of the structure 200 is uniquelydetermined by the shapes and materials of the movable plate 202 and theleaf spring portion 208. When the alternating current supplied to theflat coil 205 has the same frequency as the resonant frequency, thevibration of the movable plate 202 has the maximum amplitude.

This resonant frequency, the gain at the time of resonance, and thedeflection angle of the movable plate 202 are approximately given byequations (1), (2), and (3) described above. These equations are used asmodels for actual design.

When light from a light source is reflected by the movable plate 202 tobe scanner, the deflection angle of the light is twice the deflectionangle of the movable plate 202.

In this embodiment, since the structure 200 is integrally formed, noassembly step is required for this structure. Ultra-compact opticalscanners can be mass-produced at a low cost.

In addition, since the structure 200 is formed by using thesemiconductor manufacturing technique, a very high process precision canbe ensured. The characteristics of the optical scanner are free fromaging due to assembly errors.

The direction of the scanner in use is not fixed, and the scanner mustbe so designed as to be used in any direction. The problem in this caseis that the vibrating portion of the optical scanner is twisteddepending on the direction of the optical scanner. In this embodiment,an analysis of this problem has led to the finding that the formation ofthe through-hole 210 in the middle of the leaf spring portion 208 canrealize a structure which is resistant to the twist and provides a largedeflection angle. With the provision of the through-hole 210, thestrength characteristics of the leaf spring portion 208 are improved.

Note that since stress concentrates on the four corners of the throughhole 210, the four corners have curvatures to disperse the stress aroundthe corners.

By using a polyimide as an organic insulating material for the leafspring portion 208, the leaf spring portion 208 is resistant to brittlefracture and attains a large deflection angle while maintaining theminimum necessary strength. In addition, since the wiring layers areformed in the polyimide layer, the leaf spring portion 208 is almostfree from aging due to humidity.

Furthermore, the polyimide layer serves to insulate the wiring layers ofthe flat coil 205 from each other.

As is apparent, each arrangement of this embodiment can be variouslymodified and changed.

FIG. 9 shows a modification of this embodiment.

As shown in FIG. 9, the movable plate 202 is formed by using an organicfilm such as a polyimide layer.

Since the movable plate 202 consisting of a polyimide is smaller in massthan a plate consisting of silicon, an optical scanner using this platecan realize a large deflection angle.

The following description concerns the relationship between the mass ofthe movable plate 202 and the deflection angle.

As is apparent from equation (1) above, the mass of the movable plate202 influences the resonant frequency.

In order to increase the scanning speed of light reflected by theoptical scanner without changing the maximum deflection angle, the massof the movable plate 202 may be decreased to increase the resonantfrequency of the optical scanner.

If the material for the movable plate 202 is changed from silicon to apolyimide, the mass of the movable plate 202 decreases, and hence theresonant frequency increases.

If, however, the material for the movable plate 202 is changed fromsilicon to a polyimide, the difference in strength between the movableplate 202 and the leaf spring portion 208 decreases as compared with thecase wherein silicon is used for the movable plate 202.

This is because the relative strength of the leaf spring portion 208which supports the movable plate 202 increases.

In consideration of the manufacturing process by integral formation, itis difficult for a polyimide film to attain the thickness (300 to 500μm) of a general silicon substrate. For this reason, the difference instrength between the movable plate 202 and the leaf spring portion 208is reduced, and the movable plate 202 may deform during vibration.

Such a problem can be solved by reducing the rigidity of the leaf springportion 208 to increase the difference in strength between the movableplate 202 and the leaf spring portion 208.

The strengths of the movable plate 202 and the leaf spring portion 208are expressed by rigidities, and the rigidity of a rectangularparallelepiped member is expressed by:

G=E·b·h ³/12  (4)

where G is the rigidity, E is the Young's modulus, b is the width, and his the thickness.

As is apparent from equation (4), the difference in strength can beincreased by increasing the difference in thickness between the movableplate 202 and the leaf spring portion 208.

In consideration of the limit of the formation of a thick polyimidefilm, the thickness of the leaf spring portion 208 is preferablyreduced.

As is apparent from equation (1) above, when both the mass of themovable plate 202 and the rigidity of the leaf spring portion 208 aredecreased, the influences of the decreases in mass and rigidity on theresonant frequency cancel each other out. As a result, no greatinfluence is exerted on the resonant frequency.

As is apparent from equation (3) above, the decrease in the rigidity ofthe leaf spring portion 208 exerts a noticeable influence on changes indeflection angle.

As the rigidity of the leaf spring portion 208 decreases, the deflectionangle can be increased.

According to another modification of this embodiment, the secondpolyimide layer 207 and the third polyimide layer 209 need not beformed.

In this structure, however, since the flat coil 205 is directly exposedto the atmosphere, the optical scanner is preferably used in a vacuum toprevent an anomalous discharge between the coil portion.

According to still another modification of this embodiment, the flatcoil 205 may be formed by plating.

In order to exert a large force onto the structure, it is preferablethat the number of turns of the flat coil 205 be increased, and the coilbe finely processed.

If, however, the number of turns of the flat coil 205 is increasedwithout changing its size, the width of the wiring layer of the coildecreases to increase the wiring resistance. As a result, thetemperature of the optical scanner rises.

The strength characteristics of the leaf spring portion 208 are changedby this rise in temperature. As a result, the resonant frequency maybecome unstable.

In order to solve this problem, the thickness of the coil is preferablyincreased.

An aluminum coil pattern formed by using an electrolytic plating,sputtering, and etching is used as a seed layer to form a plating metalfilm.

According to still another modification of this embodiment, similar tothe structure shown in FIG. 6, the shape of the support member 201 maybe changed to surround the movable plate 202, and the permanent magnet211 may be fixed to the support member 201.

The mounting portion for the permanent magnet is cut by about 20 μm bydry etching. The bonding surface of the permanent magnet is coated withan adhesive or the like and bonded to the etched portion.

In this structure, since the mounting position of the permanent magnet211 is specified by etching, the permanent magnet 211 can always bemounted at the same position. In addition, the permanent magnet 211 canbe easily mounted to shorten the time required for mounting.

<Third Embodiment>

An optical scanner according to the third embodiment of the presentinvention will be described with reference to FIGS. 10, 11, and 12A to12J.

As shown in FIGS. 10 and 11, the optical scanner includes a structure300 and a permanent magnet 313.

The structure 300 is integrally formed by using the semiconductormanufacturing technique. A support member 301 and a movable plate 302are formed from a single substrate.

A single-crystal silicon substrate having a (100) plane is used for thissubstrate.

Silicon nitride films 303 are formed on the silicon substrate.

A flat coil 304 is formed on the silicon nitride film 303 on the movableplate 302.

The flat coil 304 is obtained by forming an aluminum film by sputteringand etching the film.

Contact pads 305 for contact with wiring layers 308 are arranged on thetwo end portions of the flat coil 304.

A first polyimide layer 306 is formed on the silicon nitride film 303 tocouple the support member 301 to the movable plate 302.

The wiring layers 308 are formed on the first polyimide layer 306. Oneend of the wiring layer 308 is connected to the contact pad 305, whilethe other end is located on the support member 301. An aluminumelectrode pad 309 is formed on the other end of each wiring layer 308.

A second polyimide layer 310 is formed on the first polyimide layer 306.

The second polyimide layer 310 covers the wiring layers 308 except forthe electrode pads 309 and functions as an insulating film, and alsoserves to reduce the level differences between the first polyimide layer306 and the wiring layers 308.

A third polyimide layer 311 is formed on the second polyimide layer 310.

The first polyimide layer 306, the second polyimide layer 310, and thethird polyimide layer 311 which are located between the support member301 and the movable plate 302 constitute a leaf spring portion 307 forsupporting the movable plate 302 to allow it to vibrate with respect tothe support member 301.

The third polyimide layer 311 is formed to adjust the rigidity of theleaf spring portion 307. By adjusting the thickness of the thirdpolyimide layer 311, a leaf spring portion 307 having a desired rigiditycan be obtained.

The third polyimide layer 311 is not formed on the electrode pads 309.That is, the electrode pads 309 are exposed and hence can beelectrically connected to external parts.

Note that if a leaf spring portion 307 having a desired rigidity can beobtained by using the first and second polyimide layers, the thirdpolyimide layer need not be formed.

A through hole 312 is formed in the leaf spring portion 307.

In order to realize a one-dimensional scanning operation with highlinearity, the center of the through hole 312 is preferably located inthe middle of the leaf spring portion 307 in the widthwise direction,and the through hole 107 preferably has a shape symmetrical about acentral axis perpendicular to the widthwise direction.

In addition, the through hole 312 is preferably shaped to prevent stressfrom concentrating on a specific portion upon displacement of themovable plate 105.

For the above reasons, the through hole 312 preferably has a circularshape, an elliptic shape, or a polygonal shape with round corners.

A permanent magnet 313 is positioned such that its direction ofmagnetization is roughly parallel to the vibrating direction of themovable plate 302, and the distal end of the permanent magnet upperportion is set at an arbitrary position at about 45° in the upward ordownward direction with respect to the flat coil 304 located at thedistal end portion of the movable plate 302.

A method of manufacturing the structure 300 of the optical scanner ofthis embodiment will be described next with reference to FIGS. 12A to12J.

As shown in FIG. 12A, a silicon substrate 320 having a (100) plane iscleaned first, and silicon nitride films 303 are then formed on thesurfaces of the silicon substrate 320 by using a low-pressure CVDapparatus.

The silicon nitride film 303 on the upper surface serves as an insultingfilm between a flat coil 304 to be formed on the silicon nitride film303, and the silicon substrate 320.

The silicon nitride film 303 on the lower surface is partially removedand patterned by dry etching. The patterned silicon nitride film 303servers as a mask to be used when a support member 301 and a movableplate 302 are formed from the silicon substrate 320.

As shown in FIG. 12B, a flat coil 304 is formed on the silicon nitridefilm 303 on the upper surface.

The flat coil 304 is obtained by forming an aluminum film by sputteringand patterning the film by etching.

Contact pads 305 for contact with wiring layers 308 are formed on thetwo end portions of the flat coil 304.

As shown in FIG. 12C, a mask 314 used to form a through hole 312 in aleaf spring portion 307 afterward is formed.

The mask 314 is formed by pattering a sputtered aluminum film by alift-off method or the like.

As shown in FIG. 12D, a first polyimide layer 306 is formed on thesilicon nitride film 303 on the upper surface to cover the flat coil 304and the mask 314.

The first polyimide layer 306 is formed by coating the silicon substratewith a polyimide solution, uniformly forming a polyimide film byprinting or spin coating, and sintering the film.

Subsequently, the portions of the first polyimide layer 306 which arelocated on the contact pads 305 are removed by etching.

As shown in FIG. 12E, wiring layers 308 are formed on the firstpolyimide layer 306.

Each wiring layer 308 is formed by patterning a sputtered aluminum filmby etching.

Thereafter, sputtering of aluminum and patterning may be performed againto increase the thickness of the aluminum film of each electrode pad 309on the support member 301, as needed.

As shown in FIG. 12F, a second polyimide layer 310 is formed on thefirst polyimide layer 306.

Similar to the first polyimide layer 306, the second polyimide layer 310is formed by coating the first polyimide layer 306 with a polyimidesolution, uniformly forming a polyimide film by printing or spincoating, and sintering the film.

As shown in FIG. 12G, the third polyimide layer 311 is formed on thesecond polyimide layer 310.

Similar to the first polyimide layer 306, a third polyimide layer 311 isformed by coating the second polyimide layer 310 with a polyimidesolution, uniformly forming a polyimide film by printing or spincoating, and sintering the film.

In order to increase the rigidity of the leaf spring portion 307, thethird polyimide layer 311 is formed to be thicker than the firstpolyimide layer 306 and the second polyimide layer 310.

As shown in FIG. 12H, the portions of the second polyimide layer 310 andthe third polyimide layer 311 which are located on the electrode pads309 and correspond to a through hole 312 to be formed are removed by dryetching.

As shown in FIG. 12I, the support member 301 and the movable plate 302are formed from the silicon substrate 320.

The silicon substrate 320 is anisotropically etched from its lowersurface side by using an alkaline solution and the patterned siliconnitride film 303 on the lower surface of the silicon substrate 320 as amask, thereby forming a support member 301 and a movable plate 302.

In this case, the silicon nitride film 303 under the first polyimidelayer 306 serves as a masking layer for protecting the first polyimidelayer 306 when the silicon substrate 320 is etched to form a throughhole therein.

As shown in FIG. 12J, the silicon nitride film 303 serving as a masklayer for the first polyimide layer 306 is removed by dry etching afterthe silicon substrate 320 is etched.

When the silicon nitride film 303 is removed, the aluminum mask 314appears.

The first polyimide layer 306 is removed by using this mask 314 to formthe through hole 312.

Subsequently, the mask 314 is removed by etching, and the structure 300of the optical scanner of this embodiment described above can beobtained.

The operation of the optical scanner of this embodiment will bedescribed next.

Alternating currents are supplied from a power supply (not shown) to theflat coil 304 through the electrode pads 309.

The current flowing in the flat coil 304 interacts with the magneticfield generated by the permanent magnet 313 placed near the free end ofthe structure 300. As a result, the flat coil 304, especially itsportion near the free end of the structure 300, receives the resultantforce.

Since the current flowing in the flat coil 304 is an alternatingcurrent, the direction in which the flat coil 304 receives the forceperiodically changes, and the movable plate 302 vibrates in thedirection of thickness.

The resonant frequency of the vibration of the structure 300 is uniquelydetermined by the shapes and materials of the movable plate 302 and theleaf spring portion 307. When the alternating current supplied to theflat coil 304 has the same frequency as the resonant frequency, thevibration of the movable plate 302 has the maximum amplitude.

This resonant frequency, the gain at the time of resonance, and thedeflection angle of the movable plate 302 are approximately given byequations (1), (2), and (3) described above. These equations are used asmodels for actual design.

The light reflected by the movable plate 302 is reciprocally scanned ata deflection angle twice that of the movable plate 302.

According to the optical scanner of this embodiment, since the structure300 is integrally formed, no assembly step is required for thisstructure. Ultra-compact optical scanners can be mass-produced at a lowcost.

In addition, since the structure 200 is formed by using thesemiconductor manufacturing technique, a very high dimensional precisioncan be ensured. The characteristics of the optical scanner are free fromaging due to errors between the actual dimensions and the design values.

The direction of the scanner in use is not fixed, and the scanner mustbe so designed as to be used in any direction. The problem in this caseis that the vibrating portion of the optical scanner is twisteddepending on the direction of the optical scanner. In this embodiment,an analysis of this problem has led to the finding that the formation ofthe through-hole 312 in the middle of the leaf spring portion 307 canrealize a structure which is resistant to the twist and provides a largedeflection angle. With the provision of the through-hole 312, thestrength characteristics of the leaf spring portion 307 are improved.

Note that since stress concentrates on the four corners of the throughhole 312, the four corners have curvatures to disperse the stress aroundthe corners.

By using a polyimide as an organic insulating material for the leafspring portion 307, the leaf spring portion 307 is resistant to brittlefracture and attains a large deflection angle while maintaining theminimum necessary strength.

Since the flat coil 304 and the wiring layers 308 are formed in thepolyimide film, they are almost free from aging due to humidity.

In addition, the polyimide film properly insulates the wire portions ofthe flat coil 304 from each other and the flat coil 304 from the wiringlayer 308 which extends thereon, thereby improving the performance ofthe optical scanner.

As is apparent, each arrangement of this embodiment can be variouslymodified and changed.

FIG. 13 shows a modification of this embodiment.

As shown in FIG. 13, the movable plate 302 is formed by using an organicfilm such as a polyimide layer.

Since the movable plate 302 consisting of a polyimide is smaller in massthan a plate consisting of silicon, an optical scanner using this platecan realize a large deflection angle.

The following description concerns the relationship between the mass ofthe movable plate 302 and the deflection angle.

As is apparent from equation (1) above, the mass of the movable plate302 influences the resonant frequency.

In order to increase the scanning speed of light reflected by theoptical scanner without changing the maximum deflection angle, the massof the movable plate 302 may be decreased to increase the resonantfrequency of the optical scanner.

If the material for the movable plate 302 is changed from silicon to apolyimide, the mass of the movable plate 302 decreases, and hence theresonant frequency increases.

If, however, the material for the movable plate 302 is changed fromsilicon to a polyimide, the difference in strength between the movableplate 302 and the leaf spring portion 307 decreases as compared with thecase wherein silicon is used for the movable plate 302.

This is because the relative strength of the leaf spring portion 307which supports the movable plate 302 increases.

In consideration of the manufacturing process by integral formation, itis difficult for a polyimide film to attain the thickness (300 to 500μm) of a general silicon substrate. For this reason, the difference instrength between the movable plate 302 and the leaf spring portion 307is reduced, and the movable plate 302 may deform during vibration.

Such a problem can be solved by reducing the rigidity of the leaf springportion 307 to increase the difference in strength between the movableplate 302 and the leaf spring portion 307.

The strengths of the movable plate 302 and the leaf spring portion 307are expressed by rigidities, and the rigidity of a rectangularparallelepiped member is expressed by equation (4) above.

As is apparent from equation (4), the difference in strength can beeffectively increased by increasing the difference in thickness betweenthe movable plate 302 and the leaf spring portion 307.

In consideration of the limit of the formation of a thick polyimidefilm, the thickness of the leaf spring portion 208 is preferablyreduced.

As is apparent from equation (1) above, when both the mass of themovable plate 302 and the rigidity of the leaf spring portion 307 aredecreased, the influences of the decreases in mass and rigidity on theresonant frequency cancel each other out. As a result, no greatinfluence is exerted on the resonant frequency.

As is apparent from equation (3) above, the decrease in the rigidity ofthe leaf spring portion 307 exerts a noticeable influence on changes indeflection angle.

As the rigidity of the leaf spring portion 307 decreases, the deflectionangle can be increased.

According to another modification of this embodiment, the flat coil 304may be formed by plating.

In order to exert a large force onto the structure, it is preferablethat the number of turns of the flat coil 304 be increased, and thewidth of each wire portion be small.

If, however, the number of turns of the flat coil 304 is increasedwithout changing its size, the width of each wire portion of the coildecreases to increase the wiring resistance. As a result, thetemperature of the optical scanner rises.

The strength characteristics of the leaf spring portion 208 are changedby this rise in temperature. As a result, the resonant frequency maybecome unstable.

In order to solve this problem, the thickness of the flat coil 304 ispreferably increased.

An aluminum coil pattern formed by using an electrolytic plating,sputtering, and etching is used as a seed layer to form a plating metalfilm.

FIG. 14 shows still another embodiment of this embodiment.

As shown in FIG. 14, the support member 301 is shaped to surround themovable plate 302, and the permanent magnet 313 is mounted on thesupport member 301.

The portion of the support member 301 on which the permanent magnet 313is mounted is cut to a depth of about 20 μm by dry etching. Thepermanent magnet 313 is fixed to this portion by bonding.

In this structure, since the mounting position of the permanent magnet313 is specified by etching, the permanent magnet 313 can always bemounted at the correct position. In addition, the permanent magnet 313can be easily mounted to shorten the time required for mounting.

Experiments using the optical scanner of this embodiment will bedescribed next.

FIGS. 15 and 16 show the dimensions of the structure of the opticalscanner used in the experiment.

FIG. 17 shows the relationship between the current and the deflectionangle of the optical scanner in a case wherein a rectangular wavegenerated by a pulse generator and having the same frequency as theresonant frequency is supplied to the flat coil. FIG. 18 shows therelationship between the current and the electric resistance of the flatcoil in a state wherein the optical scanner is not vibrated.

As shown in FIG. 17, it was found that the deflection angle of thisoptical scanner reaches about 40° with a current value of 10 mA. As aresult, the angle at which light was scanned reached about 80°.

The following knowledge was obtained throughout the experiments.

It was found from FIG. 17 that as the power consumption increases, therate of increase in deflection angle gradually decreases, and theresistance of the flat coil gradually increases.

It was also confirmed by another experiment that heat is generated bythe flat coil as the power consumption increased.

As shown in FIG. 18, the reason why the resistance of the flat coilincreases as the power consumption increases may be that the amount ofheat generated by the flat coil increases as the power consumptionincreases.

As shown in FIG. 17, it is taken for granted that the rate of increasein deflection angle with the increase in the amount of current decreasesbecause the leaf spring portion is affected by the heat generated by theflat coil to change the resonant frequency of the leaf spring portion.

In this experiment, since a pulse generator was used as a power supply,changes in resonant frequency could not be properly handled.

It was found from the experiment result that when the maximum currentvalue in the optical scanner used in the experiments was set to 10 mA orless, the strength of the leaf spring portion was preferably reduced toincrease the deflection angle above the angle in the experiments.

<Fourth Embodiment>

An optical scanner according to the fourth embodiment of the presentinvention will be described with reference to FIGS. 19 to 21.

In this embodiment, the optical scanner of the third embodiment furtherincorporates a strain gage, thereby providing an optical scanner inwhich a self-oscillation circuit is designed such that vibrations aremonitored by detecting the strain amount to always allow a movable platehaving a reflecting surface to vibrate at the resonant frequency.

An outline of this embodiment will be described first.

As described, in the optical scanner of the present invention, a movableplate 402 is vibrated by the interaction between the magnetic fieldgenerated by a permanent magnet 414 and the alternating current flowingin a flat coil 405.

The amplitude of the vibration of the movable plate 402 depends on therelationship between the resonant frequency of the vibration of astructure 400, which is uniquely determined by the shapes and materialsof the movable plate 402 and a leaf spring portion 403, and thefrequency of the alternating current flowing in the flat coil 405. Thisamplitude is maximized when the frequency of the alternating current isequal to the resonant frequency.

In this optical scanner, in order to maximize the deflection angle, themovable plate 402 is vibrated at the resonant frequency.

However, the resonant frequency of the optical scanner slightly changeswhen the scanner is used for a long time or the operation environmentchanges.

In order to correct this, strain gages 401 are integrally formed in theleaf spring portion 403 to detect the strain amounts, and form aself-oscillation circuit.

With this arrangement, the optical scanner of this embodiment can alwaysbe driven at the resonant frequency.

As shown in FIGS. 19 and 20, the leaf spring portion 403 of thestructure 400 is constituted by a first polyimide layer 404, wiringlayers 407, a second polyimide layer 408, and a third polyimide layer409.

The strain gages 401 are formed between the second polyimide layer 408and the third polyimide layer 409 on the leaf spring portion 403.

The strain gages 401 are formed by folding sputtered aluminum films aplurality of numbers of times in a direction parallel to the wiringlayers 407 by etching.

Signal output pads 410 are formed on the second polyimide layer 408 on asupport member 411. Wiring layers 412 extending from the strain gages401 to the signal output pads 410 are formed on the second polyimidelayer 408.

The dimensions of each strain gage 401 must be determined byanalytically calculating a resistance value required for measurement inconsideration of the influences of the strength of the leaf springportion 403.

The signal output pads 410 and the wiring layers 412 are preferablyformed to have small resistances to prevent noise in the value measuredby the strain gage 401.

For this reason, the thicknesses of the strain gages 401, the wiringlayers 412, and the signal output pads 410 are independently set.

The strain gages 401 are formed on the two sides of a through hole 413at positions separated from a central axis perpendicular to thewidthwise direction of the leaf spring portion 403 by the same distanceto prevent unstable one-dimensional vibrations.

Since only one strain gage 401 needs to be used in practice, the otherstrain gage 401 is left as a spare part.

The signals detected by these two strain gages may be compared with eachother to monitor the torsion (mode).

The operation of this embodiment will be described next.

The strain amount of the leaf spring portion 403 is measured by thestrain gage 401.

As shown in FIG. 21, the signal obtained by the strain gage 401 isamplified by a strain detection circuit 421.

The signal output from the strain detection circuit 421 is an AC signal.If, for example, the input wave is a sin wave, the signal output fromthe strain detection circuit 421 is also a sin wave.

The output signal from the strain detection circuit 421 is input to aBPF (Band Pass Filter) 422, and noise signals other than signals havingfrequencies near the resonant frequency are removed.

The phase of the signal which has passed through the BPF 422 is adjustedby a phase adjusting device 423.

The phase adjusting device 423 corrects any phase shift of the outputwaveform with respect to the input waveform while the optical scanner isvibrating at the resonant frequency, and outputs the resultant signal toan amplifier 424.

The amplifier 424 also serves as a power supply. The maximum voltagevalue of the power supply is defined to maintain the deflection angle ofthe movable plate 402 constant at the time of resonance.

The strain detection circuit 421, the BPF 422, the phase adjustingdevice 423, and the amplifier 424 constitute a self-oscillation circuit.With this circuit, the movable plate 402 is always vibrated at theresonant frequency.

According to the optical scanner of this embodiment, since the structure400 incorporating the strain gages 401 for detecting the resonantfrequency is integrally formed, no assembly step is required for thisstructure. Ultra-compact optical scanners can be mass-produced at a lowcost.

In addition, since the structure 400 is formed by using thesemiconductor manufacturing technique, a very high dimensional precisioncan be ensured. The characteristics of the optical scanner are free fromaging due to errors between the actual dimensions and the design values.

As is apparent, each arrangement of this embodiment can be variouslymodified and changed.

This embodiment may be applied to any other embodiments described above.

That is, the strain gages 401 may be arranged on the leaf spring portionof the structure of the optical scanner of each of the above embodimentsdescribed above to form a self-oscillation circuit.

The first to fourth embodiments of the present invention described aboveinclude the following devices.

(1) An optical scanner including:

a support member for fixing the scanner to a given member;

a movable plate having at least one surface serving as a reflectingsurface for reflecting light;

an elastic member which connects the support member to the movable platewhile allowing the movable plate to have single-degree-of-freedom;

a coil having at least one side formed on the movable plate; and

a permanent magnet placed near the movable plate and having a magneticfield component parallel to a direction from the movable plate to thesupport member,

the optical scanner being designed to supply an alternating current tothe coil to vibrate the movable plate with a connecting portion betweenthe elastic member and the support member serving as a fixed end,

characterized in that the elastic member incorporates an electricelement, and is an insulating elastic film extending over the movableplate and the support member.

(Corresponding Embodiment of Present Invention)

The first, second, and third embodiments

In the optical scanner according to aspect (1) of the present invention,the coil corresponds to the flat coil in each of the above embodiments.

In addition, the electric element is a general term for a flat coil, anelectric wiring layer, an electrode, a strain gage, and the like.

(Operation)

When an alternating current is supplied to a flat coil, the flat coilformed at the distal end of the movable plate generates a force basedthe interaction between the current and the magnetic field generated bythe magnet placed near the flat coil. As a result, the movable platevibrates with the connecting portion between the elastic member and thesupport member serving as a fixed end.

By supplying an alternating current having the same frequency as theresonant frequency of the optical scanner, the amplitude of theresultant one-dimensional vibration is maximized at that current value.

(Effect)

Since electric elements such as a flat coil are formed in the insulatingelastic film, the electric elements are almost free from aging due tohumidity. In addition, the electric elements and the flat coil wiringlayers can be effectively insulated from each other.

Furthermore, peeling, disconnection, and the like caused by vibrationscan be prevented.

(2) In the optical scanner according to aspect (1) of the presentinvention, the electric elements include a coil and electrodeselectrically connected thereto, the coil is formed to surround the areaextending from the movable plate to the support member, and theelectrodes are formed on the support member.

(Corresponding Embodiment of Present Invention)

The first and second embodiments

(Operation/Effect)

In the optical scanner according to aspect (2) of the present invention,the coil is a flat coil surrounding the area, inside the elastic member,which extends from the movable plate to the leaf spring portion (theportion between the support member for the elastic member and themovable plate) and the support member.

In this structure, therefore, only the coil portion formed parallel tothe end portion of the movable plate is influenced by the magnetic fluxgenerated by the permanent magnet (the force exerted on the coil portionformed on the support member has no influence on vibrations because thesupport member is fixed). For this reason, the vibrations arestabilized, and modes other than the longitudinal vibration mode arehardly generated.

In addition, since wiring layers other than the coil are not required,the manufacturing process is simple, and high productivity can beensured.

(3) In the optical scanner according to aspect (1) of the presentinvention, the electric elements include a coil, electrodes, and wiringlayers for electrically connecting the coil to the electrodes, the coilsurrounds the movable plate, and the wiring layers are formed to extendin the leaf spring portion between the support member for the elasticmember and the movable plate to electrically connect the coil to theelectrodes.

(Corresponding Embodiment of Present Invention)

The modifications of the first embodiment and the third embodiment

(Operation/Effect)

Since the wiring layers are formed in the leaf spring portion instead ofa coil, the influences of the electric elements on the leaf springportion can be easily controlled.

In addition, since the coil wiring layer is short, and the overallelectric resistance of the coil is low, the power consumption of theoptical scanner can be reduced.

(4) In the optical scanner according to aspect (2) or (3) of the presentinvention, strain gages and wiring layers for connecting signalextracting electrodes to electrodes for extracting signals from thestrain gages are formed in the insulating elastic film.

(Corresponding Embodiment of Present Invention)

The fourth embodiment

(Operation/Effect)

Since an optical scanner incorporating strain gages for detecting theresonant frequency can be integrally formed, no assembly step isrequired, and ultra-compact optical scanners can be mass-produced.

In addition, if a semiconductor manufacturing technique is used, highdimensional precision can be ensured in spite of an ultra-compactoptical scanner. The optical scanner is hardly subjected to unstablevibrations due to a problem in the manufacturing process.

(5) In any one of the optical scanners according to aspects (2), (3),and (4) of the present invention, the insulating elastic film consistsof an organic material.

(Corresponding Embodiment of Present Invention)

The first, second, and third embodiments

(Operation/Effect)

Since the organic material is used as the insulating elastic film forthe leaf spring portion, the leaf spring portion is more resistant tobrittle fracture than a leaf spring portion using an inorganic materialsuch as silicon. This leaf spring portion therefore allows a largedeflection angle while maintaining the minimum necessary strength.

(6) In the optical scanner according to aspect (5) of the presentinvention, the organic film forming the leaf spring portion isintegrally formed to cover the movable plate and the support member,

the coil is a flat coil formed by the semiconductor manufacturingtechnique to surround the areas in the elastic film and the leaf springportion on the movable plate and the area in the elastic film on thesupport member, and

the electrodes are those formed by the semiconductor manufacturingtechnique in the organic film formed on the support member, electricallyand directly connected to the flat coil, and used to connect wiringlayers for external connections.

(Corresponding Embodiment of Present Invention)

The second embodiment

(Operation/Effect)

In this structure, since the optical scanner can be integrally formed,no assembly step is required. Ultra-compact optical scanners cantherefore be mass-produced.

In addition, since the semiconductor manufacturing technique is applied,the dimensional precision of the ultra-compact optical scanner is high,and the vibrations of the optical scanner hardly become unstable due toproblems in the manufacturing process.

(7) In the optical scanner according to aspect (5) of the presentinvention, an organic film forming the leaf spring portion is integrallyformed on the movable plate and the support member by the semiconductormanufacturing technique,

the coil is a flat coil integrally formed in the insulating elastic filmformed on the movable plate by the semiconductor manufacturingtechnique, and

the electrodes are those formed in the organic film formed on thesupport member by the semiconductor manufacturing technique and servingto connect wiring layers.

(Corresponding Embodiment of Present Invention)

The third embodiment

(Operation/Effect)

With this structure, since the optical scanner is integrally formed, noassembly step is required. Ultra-compact optical scanners can thereforebe mass-produced.

Since the semiconductor manufacturing technique is applied, thedimensional precision of the ultra-compact optical scanner is high. Thevibrations of the optical scanner hardly become unstable due to problemsin the manufacturing process.

(8) In the optical scanner according to aspect (6) or (7) of the presentinvention, the movable plate and the support member are integrallyformed from a single substrate by the semiconductor manufacturingtechnique.

(Corresponding Embodiment of Present Invention)

The second and third embodiments

(Operation/Effect)

In this structure, the main portions (the support member, the movableplate, the leaf spring portion, and the electric elements) of theoptical scanner can be integrally formed by using a single substrate. Noassembly step is therefore required, and ultra-compact optical scannerscan be mass-produced.

In addition, since the semiconductor manufacturing technique is applied,the dimensional precision of the ultra-compact optical scanner is high,and the vibrations of the optical scanner hardly become unstable due toproblems in the manufacturing process.

According to the first to fourth embodiments of the present invention,the deflection angle of the optical scanner can be set to be large, andthe electric elements such as the flat coil and the wiring layers havehigh durability. Compact optical scanners can be mass-produced at a lowcost. In addition, an optical scanner which has strain gages and canscan at a stable deflection angle can be obtained.

(Fifth Embodiment)

The fifth embodiment of the present invention will be described indetail next with reference to the accompanying drawings.

FIGS. 22 to 27 show an optical scanner according to the fifth embodimentof the present invention and its modification.

The optical scanner of this embodiment is designed to scan lighttwo-dimensionally.

FIG. 22 is a perspective view showing this optical scanner. FIG. 23Ashows a driving coil used in the optical scanner. FIG. 23B is asectional view of the optical scanner. FIGS. 24A to 24E and FIGS. 25A to25D are sectional views showing the steps in manufacturing the opticalscanner.

The optical scanner of the fifth embodiment has the following structure.

This optical scanner comprises a movable plate 501, an elastic member502, a support member 503, a permanent magnet 504, and a driving coil506.

A reflecting surface 505 for reflecting light is formed on the movableplate 501. The lower surface of the movable plate 501 in FIG. 22corresponds to the reflecting surface 505.

As a main material for the movable plate 501, a material which canprevent the reflecting surface 505 from deforming during vibrations isrequired. As the main material for the movable plate 501, therefore,single-crystal silicon as a high-rigidity material is used.

The remaining materials used for the movable plate 501 include siliconnitride, aluminum, polyimides, and the like.

More specifically, the silicon nitride is used as a mask material inmanufacturing the optical scanner. The aluminum is used as a materialfor the wiring layers of the driving coil 506 and contact pads 507formed at the start and end points of the driving coil 506. In somecase, the aluminum is used as a mirror material for the reflectingsurface 505.

The polyimide is used to form films that vertically sandwich the drivingcoil 506 to insulate the wiring layers from each other and prevent theelectric elements including the contact pads 507 from being exposed tothe atmosphere.

The elastic member 502 mainly consists of a polyimide film extendingfrom the movable plate 501, and wiring layers 508 are formed in theelastic member 502 to extend from the contact pads 507 to the supportmember 503.

As the material for the wiring layers 508, aluminum is used.

The support member 503 is used as a bonding portion for fixing theoptical scanner to a die cast or the like. Bonding pads 509 forexternally supplying power to the driving coil 506 through the wiringlayers 508 are formed on the upper surface of the support member 503.

The support member 503 mainly consists of singlecrystal silicon. Sincethe single-crystal silicon has high rigidity, the support member can besuitably fixed to a die cast or the like.

The remaining materials used for the support member 503 include siliconnitride as a mask material in manufacturing the optical scanner,aluminum used to form the bonding pads 509 and the wiring layers 508,polyimide films that vertically sandwich the wiring layers 508 toprevent them from being exposed to the atmosphere, and the like.

As these polyimide films, polyimide films extending from the movableplate 501 and the elastic member 502 are used.

The single-crystal silicon used for the support member 503 and thesingle-crystal silicon used for the movable plate 501 are formed from asingle substrate.

As shown in FIG. 23A, the driving coil 506 is designed such that thewiring layer widths and the wiring layer pitches on the respective sidesdiffer from each other. More specifically, the width and pitch of thewiring layers formed near the permanent magnet 504 to be parallel to thewidthwise direction are smaller than those of the wiring layers formedon the remaining portions.

The driving coil 506 has a uniform thickness.

The permanent magnet 504 is positioned on the basis of the structuredisclosed in “TECHNICAL DIGEST OF THE SENSOR SYMPOSIUM”, 1995, pp. 17-20such that its direction of magnetization is aligned with the directionof thickness of the movable plate 501, and the distal end of thepermanent magnet lower or upper portion is set on an extended line atabout 45° in the upward or downward direction with respect to thedriving coil 506 located at the distal end of the movable plate 501.

A method of manufacturing the optical scanner of the fifth embodimentwill be described next.

FIG. 23B is a sectional view of this optical scanner, which can bemanufactured by the semiconductor manufacturing technique shown in FIGS.24A to 24E and FIGS. 25A to 25D. The optical scanner is manufactured byusing only four types of materials, namely a single-crystal siliconsubstrate, silicon nitride, a polyimide, and aluminum.

First of all, as shown in FIG. 24A, a silicon substrate 510 is cleaned,and silicon nitride films 511 are formed on the upper and lower surfacesof the silicon substrate 510 by using a low-pressure CVD apparatus.

The silicon nitride films 511 formed on the upper and lower surfaces ofthe silicon substrate 510 are used as a mask material for isolating amovable plate 501 from a support member 503. As shown in FIG. 24B, thatportion, of the silicon nitride film 511 on the lower surface, fromwhich silicon is removed is patterned by dry etching using afluorine-based gas.

As shown in FIG. 24C, a first polyimide layer 512 is formed on thesilicon nitride film 511 on the opposite surface to the patternedsurface.

The first polyimide layer 512 is formed by a method of coating thesilicon nitride film 511 with a polyimide solution, uniformly forming apolyimide film by printing or spin coating, and sintering the film.

As shown in FIG. 24D, a driving coil 506 and contact pads 507 are formedby etching the aluminum film sputtered on the first polyimide layer 512.

As shown in FIG. 24E, similar to the first polyimide layer 512, a secondpolyimide layer 513 is formed by coating the first polyimide layer 512with a polyimide solution, uniformly forming a polyimide film byprinting or spin coating, and sintering the film.

Note that the polyimide film on the contact pads 507 is removed inadvance.

As shown in FIG. 25A, wiring layers 508 are formed by etching thealuminum film sputtered on the second polyimide layer 513.

As shown in FIG. 25B, in order to ensure contact between the contactpads 507 and the driving coil 506 on the contact pads 507 and formbonding pads 509, an aluminum film is further formed by sputtering andpatterned by etching.

In this case, the aluminum film must be considerably thicker than thewiring layer 508.

As shown in FIG. 25C, a third polyimide layer 514 is formed to determinethe rigidity of the elastic member 502 and protect the bonding pads 509from the atmosphere.

After the third polyimide layer 514 is formed, the polyimide film on thebonding pads 509 is removed by a photolithographic technique and dryetching.

As shown in FIG. 25D, in order to form a movable plate 501 and a supportmember 503 from the silicon substrate 510, the silicon substrate 510 isanisotropically etched from the lower surface side by using an alkalinesolution.

In this case, as shown in FIG. 23B, the silicon nitride film 511 ispresent under the first polyimide layer 512 serving as the elasticmember 502. The silicon nitride film 511 serves as a protective layerfor protecting the first polyimide layer 512 when a through hole isformed in the silicon substrate 510 by etching.

After the through hole is formed in the silicon substrate 510 byetching, the silicon nitride film 511 exposed on the lower surfaces ofthe elastic member 502, the movable plate 501, and the support member503 is removed by dry etching.

When a reflecting surface 505 having a high reflectance is formed bysputtering aluminum on the reflecting surface, as needed, the opticalscanner of the fifth embodiment is complete.

The operation of the optical scanner of the fifth embodiment will bedescribed next.

When an alternating current is supplied through the bonding pads 509, aLorentz force is generated by the driving coil 506 wound on the distalend of the movable plate 501 owing to the interaction between thecurrent and the magnetic field generated by the permanent magnet 504.

The vector direction of this Lorentz force is determined by thepositional relationship between the permanent magnet 504 and the drivingcoil 506. In this case, the force acts in the direction of thickness ofthe movable plate 501.

Since the connecting portion between the elastic member 502 and themovable plate 501 deviates from the middle point of the movable plate501 in the widthwise direction, bending vibrations alone cannot begenerated, but both bending and torsional vibrations are generated atonce.

In this case, the vibration of the elastic member 502 in the directionof thickness with the connecting portion with respect to the supportmember 503 serving as a fixed end is referred to as the bendingvibration, and the vibration in the direction in which the movable plate501 rotates upward or downward about the central axis of the elasticmember 502 as a rotational axis is referred to as the torsionalvibration.

In this case, the amplitude of the movable plate 501 based on thebending vibration is determined by the product of the Lorentz forcegenerated by the driving coil 506 and the length of the perpendiculardropped from the point at which the Lorentz force is generated to theside of the support member 503 which is connected to the elastic member502.

In addition, the amplitude of the movable plate 501 based on thetorsional vibration is determined by the product of the Lorentz forcegenerated by the driving coil 506 and the length of the perpendiculardropped from the position at which the Lorentz force is generated to thecentral axis of the elastic member 502 in the width of direction.

The Lorentz force is determined by the performance and size of thepermanent magnet 504, the number of turns of the driving coil 506, thewiring layer length of the driving coil 506, the amount of currentsupplied to the driving coil 506, and the distance from the permanentmagnet 504 to the driving coil 506.

In this case, the driving coil 506 is formed to surround the outermostperipheral portion of the movable plate 501 to maximize the amount offorce generated.

When the support member 503 is fixed to a die cast (not shown) or thelike, and a current is supplied to the driving coil 506, the movableplate 501 starts to vibrate with the boundary portion between thesupport member 503 and the elastic member 502 serving as a fixed end.

At this time, when an alternating current having the same frequency asthe resonant frequency uniquely determined by the shapes and materialsof the movable plate 501 and the elastic member 502 is supplied, themovable plate 501 starts to vibrate at the maximum amplitude at thatcurrent value.

The vibrations in this case are two-dimensional vibrations includingboth bending and torsional vibrations, and the resonance frequencies ofboth the bending and torsional vibrations are uniquely determined by theshapes and materials of the movable plate 501 and the elastic member502.

If, therefore, the movable plate 501 is to be vibrated in the resonantstate both in the bending and twisting directions, an alternatingcurrent obtained by superimposing the current waveform for inducingresonance in the bending vibration mode on the current waveform forinducing resonance in the torsional vibration mode may be supplied tothe driving coil 506.

The optical scanner according to this embodiment is used in a state, forexample, as shown in FIG. 26. If a collimated laser beam 515 is radiatedon the reflection surface 505 of the vibrating movable plate 501, thelaser beam 515 reflected by the reflection surface 505 of the movableplate 501 is scanned two-dimensionally and a scan line 516 of a rastertype as indicated by numeral 520 is obtained. If a predetermined currentis applied from a driving circuit 519 to the driving coil 506 (see FIG.22) at a predetermined frequency, scanning can be performed at desiredfrequency and amplitude. Optical characteristics obtained along the scanline 516 are detected by a light-receiving element 517, and a detectionsignal is output to a signal processing circuit 518. The signalprocessing circuit 518 reads the optical characteristics on the scan516. Since this scanner can be remarkably reduced in size, compared tothe conventional scanner, it is suitably applied to small-sized devicesand the power consumption can be reduced.

According to the optical scanner of the fifth embodiment, therefore, thefollowing effects can be obtained.

The optical scanner of this embodiment can scan light two-dimensionally.

In this optical scanner, one driving coil 506 generates both bending andtorsional vibrations.

If, therefore, the shape of the optical scanner of this embodimentremains the same, the deflection angles in the bending and twistingdirections during operation can be uniquely determined by the currentsupplied to the driving coil 506, facilitating drive control.

In addition, since the optical scanner of this embodiment uses apolyimide film which is an organic film as the elastic member 502, thisstructure is resistant to brittle fracture, and a large deflection anglecan be obtained while the minimum necessary strength is maintained, ascompared with the structure using silicon for the vibration member likethe one disclosed in “TECHNICAL DIGEST OF THE SENSOR SYMPOSIUM”, 1995,pp. 17-20.

In addition, since the electric elements such as the driving coil 506,the wiring layers 508, and the contact pads 507 are formed in thepolyimide film, the electric elements are nearly free from aging due tohumidity. In addition, by placing the driving coil 506 in the polyimidefilm, the wiring layers of the driving coil 506 can be stably insulatedfrom each other.

Furthermore, the driving coil 506 in this embodiment is shaped to obtaina large driving force while minimizing the heat generated when a currentis supplied to the coil.

This driving force can be easily obtained by equation (5):

F=ni·B  (5)

where F is the driving force, n is the number of turns of the coil, i isthe amount of current flowing in the coil, and B is the average magneticflux density on the wiring portions of the driving coil 506 formed nearthe permanent magnet 504.

This driving force can be effectively increased by increasing the amountof current flowed to the driving coil 506. In practice, however, as theamount of current increases, more heat is generated by the driving coil506, and the electric resistance of the driving coil 506 increases. As aresult, the conversion efficiency from a current into a driving forcedeteriorates.

In addition, if the number of turns of the driving coil 506 is increasedto increase the driving force, the resistance of the driving coil 506increases. The same problem as described above is posed.

In consideration of the average magnetic flux density of the permanentmagnet 504, the distance between the permanent magnet 504 and thedriving coil 506 is preferably minimized to increase the driving force.

That is, the wiring layer width and pitch of the driving coil 506 arepreferably reduced. If, however, the width of all the wiring layers ofthe driving coil 506 is reduced, the problems associated with resistancearise as in the above case.

In order to suppress this problem, in this embodiment, as shown in FIG.23A, the width and pitch of only the wiring layers contributing to thedriving force are reduced, so that all the wiring layers concentratenear the permanent magnet 504.

In this case, the pitch of the wiring layers of the driving coil 506which do not contribute to the driving force is increased to improve themanufacturing yield of the driving coil 506.

In this embodiment, since the optical scanner can be integrally formed,almost no assembly step is required, and the productivity ofultra-compact optical scanners can be improved.

In addition, since the semiconductor manufacturing technique is used forthe optical scanner of this embodiment, the dimensional precision of theultra-compact optical scanner is high. The optical scanner is thereforefree from unstable vibrations due to problems in the respective parts orin the assembly process.

Each arrangement of this embodiment can be variously modified andchanged.

For example, as shown in FIG. 27, in order to generate torsionalvibrations with large amplitudes more reliably, a permanent magnet 521may be placed near a side wall surface 522 opposite the side wall of themovable plate 501 which is located near the portion to which the fixingframe 502 is connected.

Torsional vibrations are generated because the elastic member 502 isconnected to a portion deviated from the middle point of the movableplate 501.

The force of torsional vibrations generated is determined by the moment.In this structure, the central axis of the elastic member 502 in thewidthwise direction serves as a rotational center, and the force isgiven by the product of the length of a perpendicular dropped from theportion where the force is produced to the rotational center axis isobtained.

Since the permanent magnet 504 is positioned to have a driving forcedistribution in a direction perpendicular to the rotational center axis,a driving force for generating torsional vibrations cannot beeffectively obtained by the permanent magnet 504 alone.

The permanent magnet 521 is placed near the side wall surface 522separated most from the rotational center axis, and the driving forcegenerated by the wiring layers of the driving coil 506 which extend nearthe permanent magnet 521 is much more efficient and greater than thatgenerated by the permanent magnet 504.

In this structure, as shown in FIG. 30A, the width and pitch of thewiring layers of the driving coil 506 which are formed near thepermanent magnet 504 and the permanent magnet 521 are smaller than thoseof the remaining wiring layers.

With this setting, a driving force can be efficiently obtained, and theelectric resistance of the driving coil is minimized to minimize theheat generated when a current is supplied to the coil.

(Sixth Embodiment)

FIGS. 28 to 32B show an optical scanner according to the sixthembodiment of the present invention and its modifications.

The optical scanner of the sixth embodiment can scan lighttwo-dimensionally.

FIG. 28 is a perspective view of this optical scanner. FIG. 30B shows adriving coil used for the optical scanner.

The optical scanner of the sixth embodiment has two driving coils 606and 607 formed in areas separated from each other in the widthwisedirection of the optical scanner, unlike the fifth embodiment whichincludes the single driving coil 506.

This optical scanner comprises a movable plate 601, an elastic member602, a support member 603, a permanent magnet 604, and the driving coils606 and 607.

The movable plate 601 has a reflecting surface 605 for reflecting light.The lower surface of the movable plate 601 in FIG. 28 corresponds to thereflecting surface 605.

As a main material for the movable plate 601, a material which canprevent the reflecting surface from deforming during vibrations isrequired. As the main material for the movable plate 601, therefore,single-crystal silicon as a high-rigidity material is used.

The remaining materials used for the movable plate 601 include siliconnitride, aluminum, polyimides, and the like. More specifically, thesilicon nitride is used as a mask material in manufacturing the opticalscanner. The aluminum is used as a material for the wiring layers of thedriving coils 606 and 607 and contact pads 608 formed at the start andend points of the driving coils 606 and 607. In some case, the aluminumis used as a mirror material for the reflecting surface 605.

The polyimide films are formed to vertically sandwich the driving coils606 and 607 to insulate the wiring layers from each other and preventthe electric elements including the contact pads 608 from being exposedto the atmosphere.

The elastic member 602 mainly consists of a polyimide film extendingfrom the movable plate 601, and wiring layers 609 are formed in theelastic member 602 to extend from the contact pads 608 to the supportmember 603.

As the material for the wiring layers 609, aluminum is used.

The support member 603 is used as a bonding portion for fixing theoptical scanner to a die cast or the like. Bonding pads 610 forexternally supplying power to the driving coils 606 and 607 through thewiring layers 609 are formed on the upper surface of the support member603.

The support member 603 mainly consists of single-crystal silicon. Sincethe single-crystal silicon has high rigidity, the support member can besuitably fixed to a die cast or the like.

The remaining materials used for the support member 603 include siliconnitride as a mask material in manufacturing the optical scanner,aluminum used to form the bonding pads 610 and the wiring layers 609,polyimide films that vertically sandwich the wiring layers 609 toprevent them from being exposed to the atmosphere, and the like.

As these polyimide films, polyimide films extending from the movableplate 601 and the elastic member 602 are used.

The single-crystal silicon used for the support member 603 and thesingle-crystal silicon used for the movable plate 601 are formed from asingle substrate.

As shown in FIG. 30B, the wiring layer widths and the wiring layerpitches on the respective sides of the driving coils 606 and 607 differfrom each other.

More specifically, the width and pitch of the wiring layers of each ofthe driving coils 606 and 607 formed near the permanent magnet 604 to beparallel to the widthwise direction are smaller than those of the wiringlayers formed on the remaining portions.

Each of the driving coils 606 and 607 has a uniform thickness.

The permanent magnet 604 is positioned on the basis of the structuredisclosed in “TECHNICAL DIGEST OF THE SENSOR SYMPOSIUM”, 1995, pp. 17-20such that its direction of magnetization is aligned with the directionof thickness of the movable plate 601, and the distal end of thepermanent magnet lower or upper portion is set on an extended line atabout 45° in the upward or downward direction with respect to thedriving coils 606 and 607 located at the distal end of the movable plate601.

Note that the optical scanner of the sixth embodiment can bemanufactured by the same manufacturing method as that for the opticalscanner of the fifth embodiment.

The operation of the optical scanner of the sixth embodiment will bedescribed next.

When an alternating current is supplied through the bonding pads 610, aLorentz force is generated by the driving coils 606 and 607 wound on thedistal end of the movable plate 601 owing to the interaction between thecurrent and the magnetic field generated by the permanent magnet 604.

The vector direction of this Lorentz force is determined by thepositional relationship between the permanent magnet 604 and the drivingcoils 606 and 607.

In this case, the force acts in the direction of thickness of themovable plate 601.

If alternating currents of the same magnitude are supplied to thedriving coils 606 and 607 in the same direction, this optical scannerstarts bending vibrations with the boundary portion between the supportmember 603 and the elastic member 602 serving as a fixed end.

If alternating current of different magnitudes are supplied to thedriving coils 606 and 607 in different directions, the optical scannerstarts two-dimensional vibrations including both bending vibrations andtorsional vibrations.

In this case, the vibration of the elastic member 602 in the directionof thickness with the connecting portion with respect to the supportmember 603 serving as a fixed end is referred to as the bendingvibration, and the vibration in the direction in which the movable plate601 rotates upward or downward about the central axis of the elasticmember 602 as a rotational axis is referred to as the torsionalvibration.

In this case, the amplitude of the movable plate 601 based on thebending vibration is determined by the product of the Lorentz forcegenerated by the driving coils 606 and 607 and the length of theperpendicular dropped from the point at which the Lorentz force isgenerated to the side of the support member 603 which is connected tothe elastic member 602.

In addition, the amplitude of the movable plate 601 based on thetorsional vibration is determined by the product of the Lorentz forcegenerated by the driving coils 606 and 607 and the length of theperpendicular dropped from the position at which the Lorentz force isgenerated to the central axis of the elastic member 602 in the width ofdirection.

The Lorentz force is determined by the performance and size of thepermanent magnet 604, the number of turns of each of the driving coils606 and 607, the wiring layer length of each of the driving coils 606and 607, the amount of current supplied to each of the driving coils 606and 607, and the distance from the permanent magnet 604 to each of thedriving coils 606 and 607.

In this case, the driving coils 606 and 607 are formed to surround theoutermost peripheral portion of the movable plate 601 to maximize theamount of force generated.

When the support member 603 is fixed to a die cast (not shown) or thelike, and a current is supplied to the driving coils 606 and 607, themovable plate 601 starts to vibrate with the boundary portion betweenthe support member 603 and the elastic member 602 serving as a fixedend.

At this time, when an alternating current having the same frequency asthe resonant frequency uniquely determined by the shapes and materialsof the movable plate 601 and the elastic member 602 is supplied, themovable plate 601 starts to vibrate at the maximum amplitude at thatcurrent value.

The vibrations in this case are one-dimensional vibrations includingonly bending vibrations or two-dimensional vibrations including bothbending and torsional vibrations.

The resonance frequencies of both the bending and torsional vibrationsare uniquely determined by the shapes and materials of the movable plate601 and the elastic member 602.

If an optical scanner includes a plurality of driving coils as in thisembodiment, the vibrations obtained change in a complicated mannerdepending on the conditions of currents to be supplied.

When, for example, only bending vibrations are to be generated,alternating currents having the same frequency as the bending moderesonant frequency may be supplied to the driving coils 606 and 607.

When only torsional vibrations are to be generated, alternating currentshaving the same frequency as the torsional mode resonant frequency maybe supplied to the driving coils 606 and 607.

In this case, if the currents supplied to the driving coils 606 and 607are 180° out of phase, the movable plate 601 starts to vibrate in thetorsional mode.

When the movable plate 601 is to be vibrated in both the bending andtorsional modes in the resonant state, an alternating current obtainedby superimposing the current waveform for inducing resonance in thebending vibration mode on the current waveform for inducing resonance inthe torsional vibration mode may be supplied to each of the drivingcoils 606 and 607.

According to the optical scanner of the sixth embodiment, therefore, thefollowing effects can be obtained.

The optical scanner of this embodiment can perform both one-dimensionallight scanning using only bending vibrations and two-dimensional lightscanning using both bending and torsional vibrations. In addition, bycontrolling the magnitudes and directions of currents to be supplied tothe driving coils 606 and 607, the amplitudes of bending and torsionalvibrations can be finely controlled. Light can be scanned on even anarbitrarily determined scanning area by controlling the currents to besupplied.

Especially when the aspect ratio of the scanning area changes, theoptical scanner of the fifth embodiment cannot cope with this change,but the optical scanner of the sixth embodiment can.

In addition, since the optical scanner of the sixth embodiment uses apolyimide film which is an organic film as the elastic member 602, thisstructure is resistant to brittle fracture, and a large deflection anglecan be obtained while the minimum necessary strength is maintained, ascompared with the structure using silicon for the vibration member likethe one disclosed in “TECHNICAL DIGEST OF THE SENSOR SYMPOSIUM”, 1995,pp. 17-20.

In addition, since the electric elements such as the driving coils 606and 607, the wiring layers 609, and the contact pads 608 are formed inthe polyimide film, the electric elements are almost free from aging dueto humidity. In addition, by placing the driving coils 606 and 607 inthe polyimide film, the wiring layers of the driving coils 606 and 607can be stably insulated from each other.

Furthermore, the driving coils 606 and 607 in this embodiment is shapedto obtain a large driving force while minimizing the heat generated whena current is supplied to the coil.

This driving force can be easily obtained by equation (5) in the fifthembodiment.

For the sake of simplicity, assume that the directions and magnitudes ofthe currents supplied to the two driving coils 606 and 607 are the same.In this case, as is apparent from equation (5), the driving force can beeffectively increased by increasing the amount of current flowed to eachof the driving coils 606 and 607.

In practice, however, as the amount of current increases, more heat isgenerated by the driving coils 606 and 607, and the electric resistancesof the driving coils 606 and 607 increase. As a result, the conversionefficiency from a current into a driving force deteriorates.

In addition, if the number of turns of each of the driving coils 606 and607 is increased to increase the driving force, the resistance of eachof the driving coils 606 and 607 increases. The same problem asdescribed above is therefore experienced.

Note that, however, since the driving coils are placed in two separateareas in this embodiment, the total wiring layer length of the coils issmaller than that of the driving coil in the fifth embodiment. Thestructure of the sixth embodiment is therefore superior to that of thefifth embodiment in respect of the problem of heat.

In consideration of the average magnetic flux density of the permanentmagnet, the distance between the permanent magnet and each driving coilis preferably minimized to increase the driving force.

That is, the wiring layer width and pitch of each of the driving coils606 and 607 are preferably reduced. If, however, the width of all thewiring layers of each of the driving coils 606 and 607 is reduced, theproblems associated with resistance are posed as in the above case.

In order to suppress this problem, in this embodiment, as shown in FIG.30B, the width and pitch of only the wiring layers contributing to thedriving force are reduced, so that all the wiring layers concentratenear the permanent magnet 604.

In this case, the pitch of the wiring layers of each of the drivingcoils 606 and 607 which do not contribute to the driving force isincreased to improve the manufacturing yield of the driving coils 606and 607.

In this embodiment, since the optical scanner can be integrally formed,almost no assembly step is required, and the productivity ofultra-compact optical scanners can be improved.

In addition, since the semiconductor manufacturing technique is used forthe optical scanner of this embodiment, the dimensional precision of theultra-compact optical scanner is high. The optical scanner is thereforefree from unstable vibrations due to problems in the respective parts orin the assembly process.

As is apparent, each arrangement of this embodiment can be variouslymodified and changed.

As shown in FIG. 29, the first modification of this embodiment may havepermanent magnets 611 and 612 placed at the two ends of the movableplate 601 in the widthwise direction to reliably generate torsionalvibrations having a large amplitude.

If the permanent magnets 611 and 612 are placed such that the directionsof magnetization are set to form magnetic fields parallel to thewidthwise direction of the movable plate 601, conversion to a drivingforce can be efficiently performed.

The optical scanner of the first modification greatly differs from thestructure of the sixth embodiment in that currents must be supplied tothe driving coils 606 and 607 in different directions to generate onlybending mode vibrations.

Note that importance is attached to the efficiency in generating bendingvibrations in the structure of the sixth embodiment, whereas importanceis attached to the efficiency in generating torsional vibrations in theoptical scanner of this modification.

This difference is based on the fact that moments which influencetorsional vibrations are not uniformly distributed in the structure ofthe sixth embodiment, whereas moments for the torsional mode areuniformly distributed, and moments which influence bending vibrationsare not uniformly distributed in the structure of this modification.

In this structure, as shown in FIG. 32A, the width and pitch of thewiring layers of the driving coils 606 and 607 which are formed near thepermanent magnets 611 and 612 are smaller than those of the remainingwiring layers.

With this setting, a driving force can be efficiently obtained, and theelectric resistance of the driving coil is minimized to minimize theheat generated when a current is supplied to the coil.

As shown in FIG. 31, in order to separately control bending vibrationsand torsional vibrations more easily, the second modification of thisembodiment may have a structure similar to that of the sixth embodiment,in which the driving coils 606 and 607 are formed in two areas separatedfrom each other in the widthwise direction of the movable plate 601, andpermanent magnets 613 and 614 are placed near the driving coils 606 and607 at positions where the magnets serve to make the driving coils 606and 607 generate vibration modes corresponding to themselves.

The permanent magnet 613 corresponding to the driving coil 607 forgenerating bending vibrations is therefore placed near the distal end ofthe movable plate 601.

The driving coil 606 is formed to generate torsional vibrations. Thepermanent magnet 614 corresponding to this coil is placed near theopposite side wall surface to the side wall of the movable plate 601which is near the portion to which the permanent magnet 602 isconnected.

In this structure, since the driving coils 606 and 607 are placed in therespective vibrating directions, bending vibrations are generated when acurrent is supplied to only the driving coil 607, and torsional, albeitimperfect vibrations are generated when a current is supplied to onlythe driving coil 606.

In the sixth embodiment or its first modification, when bending andtorsional vibrations are to be generated at once, a current having awaveform obtained by superimposing the waveforms for bending andtorsional vibrations on each other is supplied to the two coils. In thismodification, however, these waveforms need not be superimposed on eachother. Instead, it suffices if alternating currents for generating therespective modes are supplied to the driving coils 606 and 607.

In this structure, the waveforms need not be superimposed on each other,and hence the electric circuit for forming current waveforms can besimplified.

In this structure, as shown in FIG. 32B, the width and pitch of thewiring layers of the driving coils 606 and 607 which are formed near thepermanent magnets 614 and 613 are smaller than those of the remainingwiring layers.

With this setting, a driving force can be efficiently obtained, and theelectric resistance of the driving coil is minimized to minimize theheat generated when a current is supplied to the coils.

(Seventh Embodiment)

FIGS. 33 to 36 show an optical scanner according to the seventhembodiment of the present invention.

The optical scanner of this embodiment can scan light two-dimensionallyand incorporates a detection coil for detecting driving frequency.

FIG. 33 is a sectional view of this optical scanner. FIG. 34 is a topview of the optical scanner.

The optical scanner incorporating the detection coil will be describedwith reference to the structure of the fifth embodiment described above.

This optical scanner comprises a movable plate 801, an elastic member802, a support member 803, a permanent magnet 804, and a driving coil805. The constituent elements of these components are the same as thosein the first embodiment.

This optical scanner includes the following electric elements: thedriving coil 805 formed on the movable plate 801; bonding pads 806formed on the support member 803; wiring layers 807 for connecting thedriving coil 805 to the bonding pads 806; and a detection coil 808extending on the movable plate 801, the elastic member 802, and thesupport member 803.

The detection coil 808 and the driving coil 805 are insulated from eachother through a second polyimide layer 810.

The detection coil 808 is sandwiched between a first polyimide layer 809and the second polyimide layer 810, and the coil wiring layers are alsoinsulated from each other by a polyimide.

Contact pads 811 are formed on the start and end points of the drivingcoil 805.

The portions, of a third polyimide layer 812 insulating the wiringlayers of the driving coil 805 from each other, which correspond to thecontact pads 811 are removed, and hence the contact pads 811 areelectrically connected to the wiring layers 807.

The wiring layers 807 are also shielded from the atmosphere by a fourthpolyimide layer 813.

The wiring layers 807 are electrically connected to the bonding pads 806through the support member 803.

Bonding pads 814 electrically connected to the start and end points ofthe detection coil 808 are formed on the support member 803.

The operation of this embodiment will be described next.

When an alternating current is supplied through the bonding pads 806, aLorentz force is generated by the driving coil 805 wound on the distalend of the movable plate 801 owing to the interaction of the current andthe magnetic field generated by the permanent magnet 804.

The vector direction of this Lorentz force is determined by thepositional relationship between the permanent magnet 804 and the drivingcoil 805. In this case, the Lorentz force acts in the direction ofthickness of the movable plate 801.

In this optical scanner, since the connecting portion between theelastic member 802 and the movable plate 801 deviates from the middlepoint of the movable plate 801 in the widthwise direction, bendingvibrations alone cannot be generated, but both bending and torsionalvibrations are generated at once.

In this case, the vibration of the elastic member 802 in the directionof thickness with the connecting portion with respect to the supportmember 803 serving as a fixed end is referred to as the bendingvibration, and the vibration in the direction in which the movable plate801 rotates upward or downward about the central axis of the elasticmember 802 as a rotational axis is referred to as the torsionalvibration.

When the movable plate 801 starts to vibrate, an induced voltage Vexpressed by equation (6) is generated:

V=B·v·l  (6)

where B is the average magnetic flux density on the coil wiring layersformed near the permanent magnet 804, y is the vibration speed of themovable plate 801, and 1 is the wiring layer length of the detectioncoil 808 for generating the induced voltage.

The voltage waveform obtained from the detection coil 808 is similar tothe vibration waveform of the movable plate 801, and the same as thewaveform of the current supplied to the driving coil 805. However, thevoltage is output out of phase with the current.

According to the optical scanner of the seventh embodiment, thefollowing effects can be obtained.

Since the detection coil 808 is integrally incorporated in the opticalscanner, the optical scanner including the detection coil 808 can beintegrally formed. For this reason, almost no assembly step is required,and the productivity of ultra-compact optical scanners can be improved.

In addition, since the semiconductor manufacturing technique is used forthe optical scanner of this embodiment, the dimensional precision of theultra-compact optical scanner is high. The optical scanner is thereforefree from unstable vibrations due to problems in the respective parts orin the assembly process.

The heat generated by the driving coil 805 has no influence on thedetection signal output from the detection coil 808 and representing thevibration state. This structure can therefore detect a signal with ahigher precision than a detection system using a strain gage and thelike.

This detection signal is used to evaluate the vibration state of themovable plate 801. In addition, a self-oscillation circuit 815 can bedesigned to allow the optical scanner to always vibrate in the resonantstate by using the detection signal, as shown in FIG. 35.

By realizing the self-oscillation of this optical scanner, stableresonance driving can always be performed without being affected bychanges in temperature and aging of the elastic member 802.

The fifth to seventh embodiments of the present invention describedabove include the following devices.

(1) An optical scanner characterized by including a support member forfixing the scanner to a given member, a movable plate having at leastone surface serving as a reflecting surface for reflecting light, anelastic member which connects the support member to the movable platewhile allowing the movable plate to have two-degree-of-freedom or more,a driving coil having at least two sides formed on the movable plate,and permanent magnets spaced apart from each other and placed near themovable plate, the optical scanner supplying an alternating current tothe coil to cause the movable plate to generate bending and torsionalvibrations with a connecting portion between the elastic member and thesupport member serving as a fixed end, wherein the elastic memberincorporates an electric element, and is an insulating elastic filmextending over the movable plate and the support member.

(Corresponding Embodiment of Present Invention)

The optical scanner according to aspect (1) of the present inventioncorresponds to the fifth embodiment.

In the optical scanner according to aspect (1) of the present invention,as in the fifth embodiment, when an alternating current is supplied tothe driving coil, the interaction between the current and the magneticfield generated by each permanent magnet generates a force that vibratesthe movable plate. As this coil, a flat coil is used in the fifthembodiment.

The electric element in the optical scanner according to aspect (1) ofthe present invention is a general term for a driving coil, a detectioncoil, a wiring layer, an electrode pad, or the like.

(Operation/Effect)

The optical scanner according to aspect (1) of the present invention hasonly one driving coil but is capable of two-dimensional driving. Inaddition, this optical scanner is a two-dimensional optical scannerwhich has a simple structure and can be easily manufactured.

Since the optical scanner according to aspect (1) of the presentinvention uses the insulating elastic film for the leaf spring portion,this structure is more resistant to brittle fracture than a structureusing silicon for a vibration member. This structure therefore allows alarge deflection angle while maintaining the minimum necessary strength.

In addition, since the electric elements are formed in the insulatingelastic film, the electric elements are almost free from aging due tohumidity. An elastic film can also be used to insulate the respectiveelectric elements.

(2) An optical scanner characterized by including a support member forfixing the scanner to a given member, a movable plate having at leastone surface serving as a reflecting surface for reflecting light, anelastic member which connects the support member to the movable platewhile allowing the movable plate to have two-degree-of-freedom or more,a plurality of driving coils each having at least one side formed on themovable plate, and permanent magnets spaced apart from each other andplaced near the movable plate, the optical scanner supplying analternating current to the coil to cause the movable plate to generatebending and torsional vibrations with a connecting portion between theelastic member and the support member serving as a fixed end, whereinthe elastic member incorporates an electric element, and is aninsulating elastic film extending over the movable plate and the supportmember.

(Corresponding Embodiment of Present Invention)

The optical scanner according to aspect (2) of the present inventioncorresponds to the sixth embodiment.

In the optical scanner according to aspect (2) of the present invention,as in the sixth embodiment, when an alternating current is supplied tothe driving coil, the interaction between the current and the magneticfield generated by each permanent magnet generates a force that vibratesthe movable plate. As this coil, a flat coil is used in the sixthembodiment.

The electric element in the optical scanner according to aspect (2) ofthe present invention is a general term for a driving coil, a detectioncoil, a wiring layer, an electrode pad, or the like.

(Operation/Effect)

The optical scanner according to aspect (2) of the present invention cancontrol the vibrations of the movable plate in a more complicated mannerby using a plurality of driving coils than the optical scanner accordingto aspect (1) of the present invention.

The scanner according to aspect (2) of the present invention can performone-dimensional driving as well as two-dimensional driving. This scannercan separately control the amplitudes of the respective modes intwo-dimensional driving by adjusting the amount of current to besupplied to each driving coil.

Since the optical scanner according to aspect (2) of the presentinvention uses the insulating elastic film for the leaf spring portion,this structure is more resistant to brittle fracture than a structureusing silicon for a vibration member. This structure therefore allows alarge deflection angle while maintaining the minimum necessary strength.

In addition, since the electric elements are formed in the insulatingelastic film, the electric elements are almost free from aging due tohumidity. An elastic film can also be used to insulate the respectiveelectric elements.

(3) The optical scanner according to aspect (1) of the present inventionis characterized in that the permanent magnets include two or morepermanent magnets, at least one permanent magnet is placed near thedistal end of the movable plate with respect to the support member, andat least one of the remaining permanent magnets is placed near a sidesurface of the movable plate.

(Corresponding Embodiment of Present Invention)

This optical scanner according to aspect (3) of the present inventioncorresponds to a modification of the fifth embodiment.

(Operation/Effect)

In the optical scanner according to aspect (3) of the present invention,the permanent magnet is placed near the side wall of the movable plateto set a large deflection angle in the twisting direction as comparedwith the structure in which the permanent magnet is placed only near thedistal end of the movable plate.

(4) The optical scanner according to aspect (2) of the present inventionis characterized in that the permanent magnets include two or morepermanent magnets, and at least two permanent magnets are placed nearthe two side wall surfaces of the movable plate.

(Corresponding Embodiment of Present Invention)

The optical scanner according to aspect (4) of the present inventioncorresponds to the first modification of the sixth embodiment.

(Operation/Effect)

In the optical scanner according to aspect (4) of the present invention,the permanent magnets are placed near the two side walls of the movableplate to set a large deflection angle in the twisting direction ascompared with the structure in which one permanent magnet is placed onlynear the distal end of the movable plate.

In the optical scanner according to aspect (4) of the present invention,however, the deflection angle in the bending direction is small. Thisstructure is therefore effective in designing an optical scanner withreference to the deflection angle in the twisting direction.

(5) The optical scanner according to aspect (2) of the present inventionis characterized in that the permanent magnets include two or morepermanent magnets, at least one permanent magnet is a permanent magnetwhich is placed near the distal end of the movable plate with respect tothe support member, and influences one of the plurality of drivingcoils, at least one of the remaining permanent magnets is a permanentmagnet which is placed near a side surface of the movable plate andinfluences one of the remaining driving coils, and the respectivepermanent magnets are placed to influence different driving coils.

(Corresponding Embodiment of Present Invention)

The optical scanner according to aspect (5) of the present inventioncorresponds to the second modification of the sixth embodiment.

(Operation/Effect)

In the optical scanner according to aspect (5) of the present invention,each permanent magnet is placed to influence only a corresponding one ofthe driving coils. For this reason, when an alternating current issupplied to one driving coil, the generated vibration mode can be almostlimited to one mode.

With the use of the structure of the optical scanner according to aspect(5) of the present invention, a current having a waveform obtained bysuperimposing the waveform for bending vibrations on the waveform fortorsional vibrations need not be supplied to each driving coil. Instead,it suffices if alternating currents for generating the respective modesare supplied to different driving coils.

The optical scanner according to aspect (5) of the present invention cantherefore simplify the arrangement of an electric circuit for generatingcurrent waveforms.

(6) The optical scanner according to each of aspects (1), (2), (3), (4),and (5) of the present invention is characterized in that the insulatingelastic film consists of an organic film.

(Corresponding Embodiment of Present Invention)

The optical scanner according to aspect (6) of the present inventioncorresponds to the fifth, sixth, and seventh embodiments.

(Operation/Effect)

Since the optical scanner according to aspect (6) of the presentinvention uses an organic film for the leaf spring portion, thisstructure is more resistant to brittle fracture than a structure usingsilicon for a vibration member. This structure therefore allows a largedeflection angle while maintaining the minimum necessary strength.

(7) The optical scanner according to each of aspects (1), (2), (3), (4),(5), and (6) of the present invention is characterized in that the widthand pitch of the wiring layers of the driving coil which are locatednear the permanent magnet are minimized.

(Corresponding Embodiment of Present Invention)

The optical scanner according to aspect (7) of the present inventioncorresponds to the fifth and sixth embodiments.

(Operation/Effect)

In the optical scanner according to aspect (7) of the present invention,the width and pitch of the coil wiring layers which are formed near thepermanent magnet and contribute to the generation of a force are reducedto allow the coil wiring layers near the permanent magnet to be placednearer to the permanent magnet, thereby obtaining a larger force than ageneral coil.

In the optical scanner according to aspect (7) of the present invention,the width and pitch of the coil wiring layers which do not contribute tothe generation of a force are set to be sufficiently large, therebysuppressing the problem of heat.

In addition, in the optical scanner according to aspect (7) of thepresent invention, the pitch of the coil wiring layers which do notcontribute to the generation of a force is set to be large so as toimprove the manufacturing yield.

(8) The optical scanner according to each of aspects (1), (2), (3), (4),(5), and (6) is characterized by including a detection coil having atleast one side integrally formed in the movable plate and used to detectthe vibration frequency of the movable plate.

(Corresponding Embodiment of Present Invention)

The optical scanner according to aspect (8) of the present inventioncorresponds to the seventh embodiment.

The detection coil in aspect (8) of the present invention is a coil forgenerating an induced electromotive force based on the interaction withthe permanent magnet as in the seventh embodiment. As this coil, theseventh embodiment uses a flat coil extending on the movable plate, theelastic member, and the support member.

(Operation/Effect)

In the optical scanner according to aspect (8) of the present invention,the heat generated by the driving coil has no influence on the signaldetected by the detection coil. This structure can therefore detect asignal with a higher precision than a detection system using a straingage and the like.

In the optical scanner according to aspect (8) of the present invention,this detection signal is used to evaluate the vibration state of themovable plate. In addition, a self-oscillation circuit can be designedto allow the optical scanner to always vibrate in the resonant state byusing the detection signal.

By realizing the self-oscillation of this optical scanner according toaspect (8) of the present invention, stable resonance driving can alwaysbe performed without being affected by changes in temperature and agingof the elastic member.

The third and fourth prior arts described above do not describe thedurability of electric elements such as the wiring layers of the opticalscanner which vibrates with large deflection angles and protectionagainst the atmosphere.

In consideration of such points, it is an object of aspects (1) to (5)of the present invention to provide an optical scanner which vibrateswith large deflection angles, and has electric elements with highdurability.

The third and fourth prior arts described above do not suggestincreasing the deflection angle of the optical scanner.

In consideration of this point, it is an object of aspect (6) of thepresent invention to provide an optical scanner which reduces therigidity of a spring portion by using an elastic film, more specificallyan organic film, for a leaf spring portion so as to obtain a largedeflection angle regardless of a decrease in the amount of forcegenerated with a reduction in the size of the scanner.

The fourth prior art described above does not describe minimizing theinfluences of heat generated when a current is flowed in the coil.

In consideration of this point, it is an object of aspect (7) of thepresent invention to provide an optical scanner having a coil shapewhich minimizes heat generated by the coil.

The third and fourth prior arts described above do not describehigh-precision detection of the device integrally formed with theoptical scanner and designed to monitor the operation state regardlessof environmental changes and aging of the optical scanner.

In consideration of this point, it is an object of aspect (8) of thepresent invention to provide an optical scanner integrally incorporatinga device which is resistant to environmental changes and can monitor thevibration state.

As described above, according to the fifth, sixth, and seventhembodiments of the present invention, there is provided an opticalscanner which vibrates with large deflection angles and has electricelements with high durability.

(Eighth Embodiment)

FIGS. 36 to 40 show an optical scanner according to the eighthembodiment of the present invention.

This optical scanner of the eighth embodiment can scan lightone-dimensionally.

FIG. 36 is a perspective view of this optical scanner. FIGS. 37 and 38are sectional views taken along a line 37-37′ and a line 38-38′ in FIG.36, respectively.

FIG. 39 shows a driving coil used for this optical scanner. FIGS. 40A to40J show the steps in manufacturing the optical scanner.

The eighth embodiment has the following structure.

This optical scanner comprises a movable plate 701, elastic members 702,support members 703, and permanent magnets 704.

A reflecting surface 705 for reflecting light is formed on the movableplate 701. The reflecting surface 705 corresponds to the lower surfaceof the movable plate 701 in FIG. 36.

As a main material for the movable plate 701, a material which canprevent the reflecting surface from deforming during vibrations isrequired.

In this case, as the main material for the movable plate 701,single-crystal silicon as a high-rigidity material is used.

The remaining materials used for the movable plate 701 include siliconnitride, aluminum, polyimide, and the like.

The silicon nitride is used as a mask material for manufacturing theoptical scanner. The residue of the silicon nitride is used to insulatethe silicon. The aluminum is used to form the wiring layers of a drivingcoil 706 and contact pads 707 at the start and end points of the drivingcoil, and may be used as a mirror material for the reflecting surface705.

Polyimide films are formed to vertically sandwich the driving coil 706to insulate the coil wiring layers from each other and prevent theelectric elements including the contact pads 707 from being exposed tothe atmosphere.

Each elastic member 702 mainly consists of a polyimide film extendingfrom the movable plate 701. Wiring layers 708 are formed in the elasticmembers 702 to extend from the contact pads 707 to the support members703.

Each wiring layer 708 consists of aluminum.

Each support member 703 is used as a bonding portion for fixing theoptical scanner to a die cast or the like. A bonding pad 709 forsupplying external power to the driving coil 706 through the wiringlayer 708 is formed on each support member 703.

The support member 703 mainly consists of singlecrystal silicon.

Since the single-crystal silicon has high rigidity, the support membercan be suitably fixed to a die cast or the like.

The remaining materials used for the support members 703 include siliconnitride as a mask material in manufacturing the optical scanner,aluminum used to form the bonding pads 709 and the wiring layers 708,polyimide films that vertically sandwich the wiring layers 708 toprevent them from being exposed to the atmosphere, and the like.

As these polyimide films, polyimide films extending from the movableplate 701 and the elastic members 702 are used.

The single-crystal silicon used for the support members 703 and thesingle-crystal silicon used for the movable plate 701 are formed from asingle substrate.

As shown in FIG. 39, the wiring layer widths and the wiring layerpitches on the respective sides of the driving coil 706 differ from eachother.

More specifically, the width and pitch of the wiring layers formed nearthe permanent magnets 704 to be parallel to the widthwise direction aresmaller than those of the wiring layers formed on the remainingportions.

The driving coil 706 has a uniform thickness.

In relation to the positions of the permanent magnets 704, this opticalscanner can be satisfactorily driven by using one permanent magnetplaced near one side wall of the movable plate. In this embodiment,however, permanent magnets are respectively placed near the two oppositeside walls of the movable plate and positioned such that the directionsof magnetization are aligned with the direction of thickness of themovable plate 701, and the distal end of the lower or upper portion ofeach permanent magnet 704 is set on an extended line at about 45° in theupward or downward direction with respect to the driving coil 706located at the distal end of the movable plate 701. This structure canfurther increase the driving force.

A method of manufacturing the optical scanner of this embodiment will bedescribed next.

This optical scanner can be manufactured by a semiconductormanufacturing method.

FIGS. 40A to 40J show the method of manufacturing this optical scanner.

This optical scanner is manufactured by using only four types ofmaterials, namely a single-crystal silicon substrate, silicon nitride, apolyimide, and aluminum.

First of all, as shown in FIG. 40A, a silicon substrate 710 is cleaned,and silicon nitride films 711 are formed by using a low-pressure CVDapparatus.

The silicon nitride films 711 formed on the upper and lower surfaces ofthe silicon substrate 710 are used as a mask material for isolating amovable plate 701 from support members 703.

As shown in FIG. 40B, that portion, of the silicon nitride film 711 onthe lower surface, from which silicon is removed is patterned in advanceby dry etching using a fluorine-based gas.

As shown in FIG. 40C, a first polyimide layer 712 is formed on thesilicon nitride film 711 on the opposite surface to the patternedsurface.

The first polyimide layer 712 is formed by a method of coating thesilicon nitride film 711 with a polyimide solution, uniformly forming apolyimide film by printing or spin coating, and sintering the film.

As shown in FIG. 40D, a driving coil 706, contact pads 707, and bondingpads 709 are formed by etching the aluminum film sputtered on the firstpolyimide layer 712.

As shown in FIG. 40E, similar to the first polyimide layer 712, a secondpolyimide layer 713 is formed by coating the first polyimide layer 712with a polyimide solution, uniformly forming a polyimide film byprinting or spin coating, and sintering the film.

Note that the polyimide film on the contact pads 707 and the boding pads709 is removed in advance.

As shown in FIG. 40F, wiring layers 708 are formed by etching thealuminum film sputtered on the second polyimide layer 713.

A third polyimide layer 714 is formed to determine the rigidity of theelastic members 702 and protect the bonding pads from the atmosphere.

As shown in FIG. 40G, after the third polyimide layer is formed, thepolyimide film on the bonding pads 709 is removed by a photolithographictechnique and dry etching.

As shown in FIG. 40H, an aluminum layer 721 is further stacked on theresultant structure by sputtering to improve the bonding characteristicsof the bonding pads 709.

As shown in FIG. 40I, in order to form a movable plate 701 and a supportmembers 703 from the silicon substrate 710, the silicon substrate isanisotropically etched from the lower surface side by using an alkalinesolution.

In this case, the silicon nitride film 711 is present under the firstpolyimide layer 712 serving as the elastic members 702. The siliconnitride film 711 serves as a protective layer for protecting the firstpolyimide layer 712 when a through hole is formed in the siliconsubstrate 710 by etching.

As shown in FIG. 40J, after the through hole is formed in the siliconsubstrate by etching, the silicon nitride film 711 exposed on the lowersurfaces of the elastic members 702, the movable plate 701, and thesupport members 703 is removed by dry etching.

Although not shown in FIGS. 40A to 40J, a dry etching process using anoxygen-based etchant is performed afterward to remove the firstpolyimide layer 712 except for the portions corresponding to the elasticmembers 702, and aluminum is sputtered on the surface for reflectinglight to form a reflecting surface having a high reflectance, thuscompleting the optical scanner of this embodiment.

The operation of the optical scanner of the this embodiment will bedescribed next.

When an alternating current is supplied through the bonding pads 709, aLorentz force is generated by the driving coil 706 wound on the distalend of the movable plate 701 owing to the interaction between thecurrent and the magnetic field generated by each permanent magnet 704.

The vector direction of this Lorentz force is determined by thepositional relationship between the permanent magnets 704 and thedriving coil 706. In this case, the force acts in the direction ofthickness of the movable plate 701.

In this optical scanner, the support members 703 are formed to surroundthe movable plate 701.

The elastic members 702 extend from the opposite two sides of themovable plate 701 to be connected to the support members 703.

The movable plate 701 can therefore generate only a torsional vibrationmode with the central axis of each elastic member 702 in thelongitudinal direction serving as a rotational axis.

Torsional vibrations are determined by the product of the Lorentz forcegenerated by the driving coil 706 near each permanent magnet 704 and thedistance from the central axis of each elastic member 702 in thelongitudinal direction to the coil near the permanent magnet 704.

The Lorentz force is determined by the performance and size of eachpermanent magnet 704, the number of turns of each driving coil 706, thewiring layer length of the driving coil 706, the amount of currentsupplied to the driving coil 706, and the distance from the permanentmagnet 704 to the driving coil 706.

The driving coil 706 is formed around the outermost periphery of themovable plate to maximize the amount of force generated.

When the support members 703 are fixed to a die cast or the like, and acurrent is supplied to the driving coil 706, the movable plate 701starts to vibrate with the boundary portions between the support members703 and the elastic members 702 serving as fixed ends.

When an alternating current having the same frequency as the resonantfrequency uniquely determined by the shapes and materials of the movableplate 701 and the elastic members 702 is supplied, the movable plate 701starts to vibrate at the maximum amplitude at that current value.

The optical scanner according to this embodiment is used in a state, forexample, as shown in FIG. 41. If a collimated laser beam 715 is radiatedon the reflection surface 705 of the vibrating movable plate 701, thelaser beam 715 reflected by the reflection surface 705 of the movableplate 701 is scanned one-dimensionally. As a result, a scan line 716 isobtained. If a predetermined current is applied from a driving circuit719 to the driving coil 706 (see FIG. 36) at a predetermined frequency,scanning can be performed at desired frequency and amplitude. Opticalcharacteristics obtained along the scan line 716 are detected by alight-receiving element 717, and a detection signal is output to asignal processing circuit 718. The signal processing circuit 718 readsthe optical characteristics on the scan 716. Since this scanner can beremarkably reduced in size, compared to the conventional scanner, it issuitably applied to small-sized devices and the power consumption can bereduced.

The optical scanner has the following effects.

The optical scanner of this embodiment can scan light one-dimensionally.

The elastic members 702 of this optical scanner pivot as torsionsprings. For this reason, unlike an optical scanner using bendingvibrations, the reflection point on the reflecting surface 705 formed onthe movable plate 701 does not move, allowing easy optical design, andimproving the uniformity in light scanning speed.

In addition, since a polyimide film which is an organic film is used forthe elastic members 702, this structure is resistant to brittlefracture, and a large deflection angle can be obtained while the minimumnecessary strength is maintained, as compared with the structure usingsilicon for the vibration member. Since the electric elements such asthe driving coil 706, the wiring layers 708, and the contact pads 707are formed in the polyimide film, the electric elements are nearly freefrom aging due to humidity. Furthermore, since the driving coil 706 isformed in the polyimide film, the wiring layers of the driving coil 706are stably insulated from each other.

The driving coil 706 in this embodiment is shaped to minimize the powerconsumption and the heat generated when a current is supplied to thecoil and obtain a large driving force.

The driving force generated by this coil is given by equation (5) above.The relationship between the current value, the power consumption, andthe heat value can be given by equations (7) and (8) below.

A power consumption P and a heat value J of the coil portion are givenby:

P=i ² R  (7)

J=i ² ·R·t  (8)

where i is the value of the current flowed to the coil, R is theelectric resistance of the coil, and t is the period of time for whichthe currents flowed to the coil.

As is apparent from equation (5) above, the driving force F can beincreased by increasing at least one of the current value i, the numbern of turns, and the magnetic flux density B.

In order to increase the number of turns and the magnetic flux density,the structure must be changed. However, the current value can be easilyincreased.

As is apparent from equations (7) and (8), as the value i of the currentflowed to the coil increases, both the power consumption P and the heatvalue J increase in proportion to the square of the current value j,resulting in undesired effects.

For this reason, the number n of turns of the driving coil 706 may beincreased, or the average magnetic flux density B may be increased bydecreasing the wiring layer width and pitch of the driving coil 706 sothat the distance between each permanent magnet and the driving coildecreases.

In either case, the resistance R of the driving coil 706 increases, andthe power consumption increases. In addition, the heat value increases.

That is, there is a trade-off relationship between the driving force F,and the power consumption P and the heat value J. In this embodiment, asshown in FIG. 37, in order to increase the driving force F whileminimizing the power consumption P and the heat value J, the width andpitch of only the wiring layers contributing to the driving force aredecreased so that the overall wiring layers concentrate near thepermanent magnet 704.

In this case, the pitch of the wiring layers of the driving coil 706which do not contribute to the driving force is increased to improve themanufacturing yield of the driving coil 706 and reduce the electricresistance of the driving coil 706.

In this embodiment, since the optical scanner can be integrally formed,almost no assembly step is required, and the productivity ofultra-compact optical scanners can be improved.

In addition, since the semiconductor manufacturing technique is used forthe optical scanner of this embodiment, the dimensional precision of theultra-compact optical scanner is high. The optical scanner is thereforefree from unstable vibrations due to problems in the respective parts orin the assembly process.

Each arrangement of this embodiment can be variously modified andchanged.

In a modification of the eighth embodiment, in order to obtain largeamplitudes, the permanent magnets 704 at the two ends may be connectedto a yoke 720, as shown in FIG. 42.

FIGS. 43 and 44 are sectional views taken along a line 43-43′ and a line44-44′ in FIG. 42, respectively.

In this case, as shown in FIG. 44, the directions of magnetization ofthe permanent magnets 704 at the two ends are set to be parallel to thewidthwise direction of the elastic member 702.

When the permanent magnets 704 are placed at the two ends through theyoke, the magnetic fluxes generated in the space between the permanentmagnets 704 can be uniformly set to be parallel to the widthwisedirection of the elastic member 702.

In addition, with the use of the yoke, the magnetic circuit becomes aclosed loop circuit, which can convert the energy of a magnetic fliedinto a driving force more efficiently than an open loop circuit like theone shown in FIG. 36. The power consumption of the driving coil cantherefore be reduced.

In the eighth embodiment, since the movable plate 701 vibrates with eachelastic member 702 serving as an axis, light is scanned onlyone-dimensionally. However, light can be scanned two-dimensionally inthe following structure. As in the prior art shown in FIGS. 48A and 48B,permanent magnets are arranged independently of the support members 703,two each of elastic members and driving coils are arranged, and theinner and outer elastic members are arranged on the support member to beperpendicular to each other.

The eighth embodiment described above includes the following aspects ofthe present invention.

(1) An optical scanner including support members for fixing the scannerto a given member, a movable plate having at least one surface servingas a reflecting surface for reflecting light, elastic members whichconnect the support members to the movable plate, a driving coil havingat least one side formed on the movable plate, and permanent magnetseach placed near the movable plate at a predetermined distancetherefrom, the optical scanner supplying an alternating current to thedriving coil to generate torsional vibrations of the movable plate withthe elastic members serving as torsion springs,

characterized in that the elastic members incorporate electric elementsand are formed from an insulating elastic film extending over themovable plate and the support members.

(Corresponding Embodiment of Present Invention)

This aspect of the present invention corresponds to the eighthembodiment.

As in the eighth embodiment, when an alternating current is supplied tothe driving coil, the interaction between the current and the magneticfield generated by each permanent magnet generates a force that vibratesthe movable plate. As this coil, a flat coil is used in the eighthembodiment.

The electric element is a general term for a driving coil, a detectioncoil, a wiring layer, an electrode pad, or the like.

(Operation/Effect)

This optical scanner is a one-dimensional optical scanner which cangenerate torsional vibrations of the movable plate, has a simplestructure, and can be easily manufactured.

Since the insulating elastic film is used for the leaf spring portion,this structure is more resistant to brittle fracture than a structureusing silicon for a vibration member. This structure therefore allows alarge deflection angle while maintaining the minimum necessary strength.

In addition, since the electric elements are formed in the insulatingelastic films, the electric elements are almost free from aging due tohumidity. An elastic film can also be used to insulate the respectiveelectric elements.

(2) The optical scanner according to aspect (1) of the present inventionis characterized in that the permanent magnets comprise at least twopermanent magnets which are placed near the opposite side wall surfacesof the movable plate.

(Corresponding Embodiment of Present Invention)

This aspect of the present invention corresponds to the eighthembodiment.

(Operation/Effect)

By placing the magnets near the two side wall surfaces of the movableplate, a larger deflection angle can be realized.

(3) The optical scanner according to aspect (2) of the present inventionis characterized in that at least the two permanent magnets areconnected through a yoke.

(Corresponding Embodiment of Present Invention)

This aspect of the present invention corresponds to a modification ofthe eighth embodiment.

(Operation/Effect)

In this optical scanner, the two magnets placed near the two side wallsurfaces are connected through the yoke to realize an ideal magneticfield distribution near the driving coil which influences the drivingforce generated by the driving coil. In addition, unlike a structureusing no yoke, this structure can efficiently convert magnetic fieldsinto a driving force because the magnetic fields concentrate near thedriving coil.

(4) The optical scanner according to each of aspects (1), (2), and (3)is characterized in that the insulating elastic film consists of anorganic film.

(Corresponding Embodiment of Present Invention)

This aspect of the present invention corresponds to the eighthembodiment.

(Operation/Effect)

Since an organic film is used for the leaf spring portion, thisstructure is resistant to brittle fracture, and a large deflection anglecan be obtained while the minimum necessary strength is maintained, ascompared with the structure using silicon for the vibration member

(5) The optical scanner according to each of aspects (1), (2), and (3)is characterized in that the wiring layer width and pitch of the drivingcoil are minimized near each permanent magnet.

(Corresponding Embodiment of Present Invention)

This aspect of the present invention corresponds to the eighthembodiment.

(Operation/Effect)

The width and pitch of the coil wiring layers which are formed near thepermanent magnet and contribute to the generation of a force are reducedto allow the coil wiring layers near the permanent magnet to be placednearer to the permanent magnet, thereby obtaining a larger force than ageneral coil.

The width and pitch of the coil wiring layers which do not contribute tothe generation of a force are set to be sufficiently large, therebysuppressing the problem of heat.

In addition, the pitch of the coil wiring layers which do not contributeto the generation of a force is set to be large so as to improve themanufacturing yield.

As has been described in detail above, according to the eighthembodiment of the present invention, there is provided an opticalscanner which vibrates at a large deflection angle and has electricelements with high durability.

(Ninth Embodiment)

An optical scanner according to a ninth embodiment of the presentinvention will now be described with reference to FIGS. 49-51, 52A-52Iand 53-56.

FIG. 49 is a perspective view showing the structure of the opticalscanner according to the ninth embodiment, FIG. 50 is a sectional viewtaken along a line A—A or a central axis of the optical scanner in FIG.49, and FIG. 51 is a sectional view taken along a line B—B in FIG. 49.FIGS. 52A to 52I are views showing the manufacturing process for theoptical scanner according to the ninth embodiment, FIG. 53 is a viewshowing the operational state of the optical scanner according to theninth embodiment, and FIGS. 54 to 56 show modifications of the opticalscanner according to the ninth embodiment.

As is shown in FIG. 49, the optical scanner according to this embodimentcomprises a structure 1100 capable of vibrating its free end in adirection of arrow V, and a permanent magnet 1150 disposed to face thefree end of the structure 1100. The structure 1100 comprises a supportmember 1110 provided at a fixed end of the structure 1100, a movableplate 1120 disposed at the free end and provided with a reflectionsurface serving as a mirror, and a leaf spring-like elastic member 1130for coupling the support member 1110 and movable plate 1120. The movableplate 1120 is provided with a coil 1140 such that the coil 1140 runsaround a peripheral portion of the movable plate 1120. Wiring 1141 isformed to extend over the coil 1140 from a coil end portion located atan innermost turn of the coil 1140. The wiring 1141 is connected to anelectrode pad 1145 via wiring 1142 provided on the elastic member 1130.On the other hand, a coil end portion located at an outermost turn ofthe coil 1140 is connected to an electrode pad 1146 via wiring 1143provided on the elastic member 1130. In the manufacturing process of theoptical scanner, the wiring 1143 and wiring 1142 are formed at the sametime. Thus, the wiring 1143 and the associated coil end portion areconnected via a stepped portion 1144. A through-hole is formed in theelastic member 1130.

The direction magnetization of the permanent magnet 1150 issubstantially parallel to the direction of vibration of the movableplate 1120. The permanent magnet 1150 is positioned such that a lowerend portion or an upper end portion of the permanent magnet 1150 isopposed to the free end of the movable plate 1120 along a line extendedfrom the plane of the coil 1140 at about 45° upward or downward. Inorder to achieve one-dimensional scan with high linearity, thethrough-hole 1160 should preferably be formed such that the center ofthe through-hole 1160 is positioned at the center of the width of theelastic member 1130 and that the through-hole 1160 is line-symmetricwith respect to a center axis (A—A line in FIG. 49) extendingperpendicular to the width of the elastic member 1130. Moreover, thethrough-hole 1160 should preferably be formed in such a shape (e.g.circular, oval, or polygonal with rounded corners) that no stressconcentrates at a specification point when the free end of the structure1100 is vibrating.

The cross-sectional structures of the optical scanner, along lines A—Aand B—B in FIG. 49, will now be described with reference to FIGS. 50 and51.

As is shown in FIG. 50, when the optical scanner is viewed in crosssection along line A—A in FIG. 49, the support member 1110 comprises alamination of a silicon substrate 1200, a silicon nitride film 1210, afirst polyimide layer 1220, a second polyimide layer 1230 and a thirdpolyimide layer 1240. The movable plate 1120 further includes a coil1140 provided on the first polyimide layer 1220 in addition to thestructure of the support member 1110. The elastic member 1130 comprisesa lamination of the first polyimide layer 1220, second polyimide layer1230 and third polyimide layer 1240. The through-hole 1160 is formed inthe elastic member 1130 and penetrates these layers. The siliconsubstrate 1200 is formed of using a silicon single-crystal substratewith plane direction (100). Polyimide is an organic insulating materialwith elasticity, and its elastic coefficient is much lower than that ofthe silicon single-crystal substrate. Thus, the first to third polyimidelayers serve as elastically deformable thin films.

As is shown in FIG. 51, when the support member 1110 is viewed in crosssection along B—B in FIG. 49, the wiring 1142 is provided on the secondpolyimide layer 1230, and the electrode pad 1145 is provided on thewiring 1142. A through-hole is formed in the third polyimide layer 1240at the location of the electrode pad 1145. The wiring 1141 extendingover the coil 1140 is provided on the second polyimide layer 1230. Thefirst polyimide layer 1220 is provided with a stepped portion 1147 forconnecting the wiring 1141 and coil 1140. A through-hole is formed inthe second polyimide layer 1230 at the location of the stepped portion1147. In the elastic member 1130, the wiring 1142 is provided on thesecond polyimide layer 1230.

The thickness of the third polyimide layer 1240 is made substantiallyequal to the sum of the thicknesses of the first and second polyimidelayers 1220 and 1230. In the present invention, accordingly, the coil1140 provided within the second polyimide layer 1230 is located at aposition where the thickness of the elastic member 1130 is substantiallyhalved (i.e. the thickness being halved in the direction of laminationof respective layers).

The operation of the optical scanner having the above structure will nowbe described.

An AC is supplied from a power supply (not shown) to the coil 1140 viathe electrode pads 1145 and 1146. If current flows through the coil1140, a force in a predetermined direction acts on the coil 1140 owingto an interaction between a magnetic field produced by the permanentmagnet 1150 and the current flowing in the coil 1140. In particular,force acts on that portion of the coil 1140, which is located near thefree end of the structure 1100. In this case, the permanent magnet 1150and part of the coil 1140 function as an actuator. Since the currentflowing in the coil 1140 is an AC, the direction of force acting on theplanar coil 1140 changes periodically. Those portions of the first tothird polyimide layers, which are not fixed on the silicon substrate1200, have relatively low rigidity, and thus these portions serve asleaf spring-like elastic member 1130. As a result, the movable plate1120 vibrates in its thickness direction. The resonant frequency of thestructure 1100 is definitively determined by the shape and material ofthe movable member 1120 and elastic member 1130. If an AC of a frequencyequal to the resonant frequency is supplied to the coil 1140, themovable plate 1120 vibrates at a maximum amplitude on the basis of thevalue of the supplied current. If light is radiated on the reflectionsurface of the thus vibrating movable plate 1120, the light reflected bythe reflection surface of the movable plate 1120 is reciprocally scannedin a deflecting direction determined by the deflection angle of themovable plate 1120.

A process for manufacturing the structure 100 of the optical scanneraccording to this embodiment will now be described with reference toFIGS. 52A to 52I.

A silicon substrate 1200 with plane direction (100) is prepared, asshown in FIG. 52A. The silicon substrate 1200 is cleaned and siliconnitride films 1210 are formed on an obverse and a back surface of thesilicon substrate 1200 by using a low-pressure CVD apparatus. Portion ofthe silicon nitride film 1210 on the back surface is removed andpatterned by dry etching. The patterned silicon nitride film 1210 servesas a mask for forming the support member 1110 and movable plate 1120from the silicon substrate 1200. On the other hand, the silicon nitridefilm 1210 on the obverse surface serves to protect the structure formedon this silicon nitride film 1210 in the process (i.e. etching process)for forming the support member 1110 and movable plate 1120 from thesilicon substrate 1200.

In FIG. 52B, a first polyimide layer 1220 is formed on the front-sidesilicon nitride film 1210. The first polyimide layer 1220 is formed byapplying a polyimide solution on the silicon substrate, uniformlyforming a film of polyimide solution by means of a screen printingmethod or a spin coating method, and then curing the same.

In FIG. 52C, a coil 1140 of a predetermined pattern on the firstpolyimide layer 1220. The coil 1140 is formed in a predetermined patternby sputtering aluminum on the first polyimide layer 1220 and selectivelyetching the aluminum.

In FIG. 52D, a second polyimide layer 1230 is formed on the firstpolyimide layer 1220 so as to cover the coil 1140. The second polyimidelayer 1230, like the first polyimide layer 1220, is formed by applying apolyimide solution on the first polyimide layer 1220, uniformly forminga film of polyimide solution by means of a screen printing method or aspin coating method, and then curing the same.

In FIG. 52E, wiring 1142, 1143 (see FIG. 49) is formed on the secondpolyimide layer 1230. The wiring 1142, 1143 is formed in a predeterminedpattern by sputtering aluminum on the second polyimide layer 1230 andselectively etching the aluminum. In this wiring forming step, thewiring 1142 needs to be formed to extend over the planar coil 1140 (seeFIG. 52C). For this purpose, a polyimide portion located at the innercoil end portion of the coil 1140 is first etched away, and thenaluminum is formed and patterned in the space from which the polyimidewas etched away. Thus, a contact portion between the layers (i.e. thestepped portion 1147 in FIG. 51) is formed. Subsequently, aluminum isformed and patterned on the second polyimide layer 1230. In this step,the stepped portion 1144 (see FIG. 49), too, is similarly formed.

In FIG. 52F, a third polyimide layer 1240 is formed on the secondpolyimide layer 1230. The third polyimide layer 1240, like the first andsecond polyimide layers 1220 and 1230, is formed by applying a polyimidesolution on the second polyimide layer 1230, uniformly forming a film ofpolyimide solution by means of a screen printing method or a spincoating method, and then curing the same. The third polyimide layer 1240functions to provide predetermined characteristics to the elastic member1130 and to prevent the wiring 1142, 1143 (see FIGS. 49 and 52E) frombeing exposed to air and degraded with the passing of time. Thethickness of the third polyimide layer 1240 is made substantially equalto the sum of thicknesses of the first and second polyimide layers 1220and 1230. In the finished state, the wiring 1142, 1143 provided withinthe elastic member is located at a position where the thickness of theelastic member is substantially halved.

In FIG. 52G, those portions of the first to third polyimide layers 1220,1230 and 1240, which are located on the electrode pads 1145 and 1146(see FIG. 49) and correspond to the position of the through-hole 1160,are removed by dry etching.

In FIG. 53H, in order to form the elastic member 1130, the reverse sideof the silicon substrate 1200 is subjected to anisotropic etching withuse of an alkali solution, while the silicon nitride film 1210 patternedon the back surface of the silicon substrate 1200 is being used as amask. At this time, the silicon nitride film 1210 lying under the firstpolyimide layer 1220 serves as a mask for protecting the first polyimidelayer 1220, when the silicon substrate 1200 is etched.

After the silicon substrate 1200 is etched, the silicon nitride film1210 used as a mask for the first polyimide layer 1220 is removed by dryetching, as shown in FIG. 52I. Thus, the structure 1100 of the opticalscanner of the present embodiment is obtained.

According to the optical scanner of the above-described embodiment, thestructure 1100 can be formed integrally through the series ofmanufacturing steps. Accordingly, the assembling work is not needed andthe very small optical scanner can be mass-produced at low cost. Sincethe structure 1100 is manufactured by applying semiconductormanufacturing techniques, precision in dimension is very high. Thus,optical scanners with very low variance in characteristics can bemanufactured. Since polyimide or organic insulating material is used asmaterial of the elastic member 1130, the possibility of occurrence offragile-destruction is low and a large deflecting angle is obtained.Moreover, since the coil 1140 and wiring 1142, 1143 are not exposed tothe surface of polyimide and are formed within the elastic member 1130,degradation with the passing of time, such as oxidation due to moisture,can be prevented.

In this embodiment, the wiring 1142, 1143 is located at a position wherethe thickness of elastic member 1130 is substantially halved. Ingeneral, in the operation of the optical scanner, the elastic member1130 greatly deforms and has a large stress. In this embodiment, themovable plate 1120 is driven by mainly utilizing bending deformation ofthe leaf spring or elastic member 1130. In this case, a tensile stressoccurs at the surface of the elastic member 1130 which deforms in aconvex shape, and a compression stress occurs at the surface whichdeforms in a concave shape. It is thus understood that there is apredetermined portion of the leaf spring in its thickness direction,where substantially no stress occurs. If the elastic characteristics ofthe elastic member 1130 are uniform in its thickness direction, thestress at a position where the thickness of elastic member 1130 issubstantially halved is nearly zero.

If the wiring is located at the surface of the elastic member as in theprior art, the wiring is present at the position where the stress ishigh. In this case, if the elastic member is driven repeatedly, thewiring may be broken due to fatigue. By contrast, in this embodiment,the elastic member 1130 has a laminated structure and the wiring 1142,1143 is disposed at a position where the thickness of the elastic member1130 is substantially halved. Accordingly, even if the elastic member isdriven repeated for a long time period, breakage of wiring due tofatigue does not occur and the reliability of the optical scanner can bemaintained. In order to obtain these advantages, it is ideal that thewirings 1142 and 1143 are formed at the same position in the thicknessdirection. In other words, it is ideal that the wirings 1142 and 1143are formed on the same layer in the laminated structure fabricated inthe semiconductor process. To achieve this idea, the stepped portion1144 is formed between the coil 1140 and wiring 1143 in this embodiment.

The optical scanner of this embodiment is used, for example, in thestate shown in FIG. 53. If a collimated laser beam is radiated from alaser source 1300 onto the reflection surface of the vibrating movableplate 1120, the laser beam reflected by the reflection surface of themovable plate 1120 is scanned one-dimensionally and a scan line 1302 isobtained. Scanning at a desired frequency and amplitude can be made byapplying a predetermined current with a predetermined frequency to thecoil 1140 (see FIG. 49) as a drive signal. Compared to the conventionalscanner, this optical scanner can be greatly reduced in size. Thus, thisoptical scanner is suitably applied to small devices, and powerconsumption can be reduced.

The optical scanner according to this embodiment is normally driven at apredetermined resonant frequency in order to obtain a maximum scanamplitude. The resonant frequency is definitively determined by theshape and material of the movable plate 1120 and elastic member 1130.Strictly speaking, the resonant frequency is slightly influenced by themechanical characteristics of the wiring disposed within the elasticmember. Since in this embodiment the wiring is located at a positionwhere the thickness of the elastic member is substantially halved, thereis an advantage in that the resonant frequency is less influenced by themechanical characteristics of the wiring.

The structures of this embodiment are not limited to those describedabove, and various modifications can be made. For example, the planarcoil 1140 may be formed by plating, and not by sputtering and etching.In particular, when a large deflection angle is required, the number ofturns of the coil needs to be increased. If the number of turns alone isincreased without increasing the cross-sectional area of the coil, theresistance value of the coil increases and consequently the power supplyvoltage and power consumption increase. If the coil is formed byplating, however, the thickness of the coil can be made greater than inthe case of the sputtering and desired specifications can be achieved.

The coil shape is not limited to the above-described one in which thecoil runs around the peripheral portion of the movable member. Forexample, as shown in FIG. 54, the coil may run around the peripheralportion of the structure 1100 including the movable plate 1120 and 1110.In this modification, the number of wiring portions extending on theelastic member 1130 increases, and it becomes more important to keep thereliability of each wiring portion. In this case, the advantages of theabove-described embodiment can be obtained by situating the respectivewiring portions at a position where the thickness of the elastic memberis substantially halved. In this modification, however, there is noclear distinction between the coil and wiring. Part of the coilfunctions both as an actuator and as wiring, and the stepped portion isnot needed. Thus, the coil and wiring may be formed between the firstpolyimide layer and second polyimide layer, and the step of forming thethird polyimide layer may be omitted. In this case, if the thickness ofthe first polyimide layer is made equal to that of the second polyimidelayer, the coil and wiring can be situated at a position where thethickness of the elastic member is substantially halved.

The method of driving in this embodiment is not limited to the methodwherein the AC with the frequency equal to the resonant frequency of theoptical scanner is used to reciprocally drive the movable plate 1120.For example, the movable plate 1120 may be statically positioned by adriving method using, e.g. a variable frequency or a DC.

In this embodiment, the optical scanner using the actuator comprisingthe permanent magnet 1150 and coil 1140 has been described. The presentinvention is also applicable to a modification as shown in FIGS. 55 and56, wherein the optical scanner uses an electrostatic actuator.

In the optical scanner of this modification, a movable electrode 1170 isprovided on the surface of the movable plate 1120, and a stationaryelectrode 1180 opposed to the movable electrode 1170 is fixed on a fixedmember (not shown). The movable electrode 1170 is electricallyconnectable to an external power supply 1195 via an electrode pad 1190,wirings 1142 and 143, and interlayer wirings 1171 and 1172. In thisstructure, if a potential difference is provided by the power supply1195 between the electrode pad 1190 and stationary electrode 1180,electrostatic attractive force occurs between the stationary electrode1180 and movable electrode 1170 and the movable plate 1120 is driven.Since the electrostatic attractive force is inversely proportional tothe square of an inter-electrode distance, it is desirable that thestationary electrode 1180 and movable electrode 1170 be arranged at aclosest possible distance. In this modification, as shown in FIG. 56,the movable electrode 1170 is formed on the surface of the movable plate1120 opposed to the stationary electrode 1180, and the wirings 1142 and1143 are situated at a position where the thickness of the elasticmember 1130 is substantially halved. As a result, like the opticalscanner using the actuator comprising the permanent magnet and coil, thestress occurring at the wiring due to deformation of the elastic member1130 can be reduced and the reliability enhanced.

(Tenth Embodiment)

An optical scanner according to a tenth embodiment of the presentinvention will now be described with reference to FIGS. 57-60, 61A-61Jand 62-68.

FIG. 57 is a perspective view showing the structure of the opticalscanner according to the tenth embodiment, FIG. 58 is a sectional viewtaken along a line A—A in FIG. 57, and FIG. 59 is a sectional view takenalong a line B—B in FIG. 59. FIG. 60 is a plan view of the movable plateand elastic members. FIGS. 61A to 61J are views showing themanufacturing process. FIGS. 62 to 65 show simulation results of stressacting on the wiring of the optical scanner. FIG. 66 shows the opticalscanner as applied to a laser scanning microscope, and FIGS. 67 and 68show optical scanners according to modifications of the tenthembodiment.

As is shown in FIGS. 57, 58 and 59, the optical scanner according tothis embodiment comprises a structure 1400 and permanent magnets 1404.The structure 1400 comprises a movable plate 1401, leaf spring-like ortorsion-bar-like elastic members 1402, and a support member 1403. Themovable plate 1401 is coupled on both sides to the support member 1403by two elastic members 1402 such that the movable plate 1401 issupported on both sides. A reflection surface 1405 for reflecting lightis formed on the movable plate 1401. In FIG. 57, the reflection surface1405 is formed on the back surface of the movable plate 1401.

A drive coil 1406 is formed on a peripheral portion of the movable plate1401. A vibration detection coil 1426 is formed inside the drive coil1406. When the movable plate 1401 is vibrated, a signal proportional tothe vibration velocity of the movable plate 1401 is obtained from thevibration detection coil 1426. It is preferable that the movable plate1401 be formed mainly of such a material that the reflection surfacewill not deform during vibration. In this embodiment, as a main materialof the movable plate 1401, single-crystal silicon (plane direction:(100)) which is a high-rigidity material is used. In addition to thesingle-crystal silicon, silicon nitride material, aluminum material andpolyimide material are used in the movable plate 1401.

The silicon nitride material is a residual of material used as a mask infabrication of the optical scanner, and is used as an insulatingmaterial for silicon. The aluminum material is used for wiring of thedrive coil 1406, electrode pads 1407 at the beginning and end points ofthe drive coil, wiring for the detection coil 1426, and electrode pads1427 at the beginning and end points of the detection coil. In addition,the aluminum material is used as mirror material for forming thereflection surface 1405, where necessary. The polyimide material is usedto sandwich the drive coil 1406 and detection coil 1426 from above andbelow. The polyimide material insulates the coil and wiring and preventselectric elements including electrode pads 1407 and 1427 from contactingair.

The elastic members 1402 are formed mainly of polyimide film extendingfrom the movable plate 1401. As is shown in FIG. 57, one of the twoelastic members 1402 and the other are provided on the right and leftsides of the movable plate 1401, respectively. Four wiring elements 1408extending from the electrode pads 1407 and 1427 to the support member1403 are formed inside the elastic member 1402 on the right side in FIG.57. These wiring elements 1408 are formed of aluminum material. On theother hand, dummy wiring elements 1428 connected to nowhere are formedinside the elastic member on the left side of FIG. 57. The right andleft elastic members 1402 thus have substantially equal mechanicalcharacteristics.

The support member 1403 formed to surround the movable plate 1401 isused as an attachment portion for attaching the optical scanner to theoutside. Four electrode pads 1409 for supplying external power to thedrive coil 1406 and detection coil 1426 via the wiring 1408 are formedon the support member 1403. In this embodiment, the four electrode pads1409 are all provided on the same side (the right side in the figure) onthe support member 1403 and are arranged close to one another. As aresult, the four electrode pads 1409 can be connected to the outside inone step, for example, by using a flexible printed board.

The support member 1403 is formed mainly of single-crystal silicon. Thesingle-crystal silicon has high rigidity and is suitable for fixation onthe outside. Silicon nitride material, aluminum material and polyimidefilms are also used in the support member 1403. The silicon nitridematerial is used as mask material in fabrication of the optical scanner,the aluminum material is used to form the electrode pads 1409 and wiringelements 1408 and 1428, and the polyimide films are used to sandwich thewiring 1408 from above and below and to prevent it from contacting air.The polyimide films extend from the movable plate 1401 and elasticmember 1402. The single-crystal silicon of support member 1403 and thatof the movable plate 1401 are formed of the same substrate.

In the optical scanner of this embodiment, the two permanent magnets1404 are disposed on the support member 1403 so as to be opposed tovibration ends of the movable plate 1401. The direction of magnetizationof each permanent magnet 1404 is parallel to the thickness direction ofthe movable plate 1401. The permanent magnets 1404 are positioned suchthat their lower end portions or upper end portions are opposed to thevibration ends of the movable plate 1401 along lines extended from theplane of the drive coil 1406 at about 45° upward or downward.

FIG. 60 is a plan view of the movable plate 1401 and elastic members1402. FIG. 60 also shows the drive coil 1406, detection coil 1426 andwirings 1408 and 1428 for the purpose of convenience. The drive coil1406 is provided on a peripheral portion of the movable plate 1401, andthe detection coil 1426 is formed inside the drive coil 1406. All fourlead wires 1408 connecting the movable plate and support member via theinside of the elastic member 1402 pass through the elastic member 1402on the right side in FIG. 60. On the other hand, four dummy wiringelements 1428 are formed in the elastic member 1402 on the left side inFIG. 60.

Each elastic member 1402 in this embodiment are formed of a plurality ofpolyimide layers. The wirings 1408 and 1428 are formed between polyimidelayers at a position where the thickness of the elastic member 1402 issubstantially halved. The wiring elements 1402, 1428 are arrangedsymmetrical and close to one another with respect to a position wherethe elastic member 1402 is substantially divided into two in its widthdirection.

The operation of the optical scanner according to this embodiment willnow be described.

If an AC is supplied to the drive coil 1406 from the two electrode pads1409, a Lorentz's force occurs in the drive coil 1406 due to aninteraction between the drive coil 1406 and permanent magnets 1404. Thedirection of the force is determined by the positional relationshipbetween the permanent magnets 1404 and drive coil 1406. In this case,the force occurs in the thickness direction of the movable plate 1401.Accordingly, the basic vibration of the movable plate 1401 is atorsional vibration about a longitudinal center axis extending throughthe two elastic members 1402. The moment for causing the torsionalvibration is determined by a product (Lorentz's force X distance) of theLorentz's force produced in the drive coil 1406 near the permanentmagnets 1404 and the distance between the longitudinal center axis ofthe two elastic members 1402 and the drive coil 1406 near the permanentmagnets 1404. The Lorentz's force is determined by the characteristicsof the permanent magnets 1404, the number of turns of the drive coil1406, the length of wiring, the current, the distance between thepermanent magnets 1404 and the drive coil 1406, etc. The drive coil 1406is formed around the outermost peripheral portion of the movable plate1406 in order to increase the Lorentz's force and moment as much aspossible.

If an AC is supplied to the drive coil 1406 in the state in which thesupport member 1403 is fixed to the outside, the movable plate 1401vibrates, with the center of vibration being at boundary portionsbetween the support member 1403 and elastic members 1402. In this case,the permanent magnets 1404 and the portions of the drive coil 1406,which are opposed to the permanent magnets 1404, function as anactuator. If an AC having a frequency equal to the resonant frequencydetermined definitively by the shape and material of the movable plate1401 and elastic members 1402 is applied to the movable plate 1401, themovable plate 1401 begins to vibrate at a maximum amplitudecorresponding to the value of the AC.

On the other hand, if the movable plate 1401 vibrates, the vibrationdetection coil 1426 moves within the magnetic field produced by thepermanent magnets 1404. At this time, an electromotive force occurs inthe vibration detection coil 1426 due to electromagnetic induction. Thepolarity of the electromotive force is determined by the direction ofmovement of the vibration detection coil 1426, and the absolute value ofthe electromotive force is determined by the magnetic flux density, thenumber of turns of the coil, the velocity of movement of the coil, thelength of coil within magnetic field, etc. Accordingly, a signalproportional to the vibration velocity of the movable plate 1401 isoutput from the vibration detection coil 1426, and the condition ofvibration can be monitored or controlled on the basis of this signal.

The method of manufacturing the optical scanner according to the presentembodiment will now be described with reference to FIGS. 61A to 61J.

This optical scanner can be manufactured by semiconductor fabricationtechniques. A silicon substrate 1410 is cleaned and silicon nitridefilms 141 are formed on an obverse and back surface of the siliconsubstrate 1410 by using a low-pressure CVD apparatus (FIG. 61A). Thesilicon nitride films 1411 formed on the obverse and back surfaces ofsilicon substrate 1410 are used as masks for separating the movableplate 1401 and support member 1403. For this purpose, a portion (forremoving silicon) of the reverse-side silicon nitride film 1411 isremoved in advance by dry etching using fluorine-based material (FIG.61B). Subsequently, a first polyimide layer 1412 is formed on thefront-side silicon nitride film 1411 (FIG. 61C). The first polyimidelayer 1412 is formed by applying a polyimide solution on the siliconnitride film 1411, uniformly forming a film of polyimide solution bymeans of a screen printing method or a spin coating method, and thencuring the same.

After sputtering aluminum material on the first polyimide layer 1412,the aluminum material is etched to form the drive coil 1406, detectioncoil 1426 and electrode pads 1407, 1427 and 1409 (FIG. 61D).

Subsequently, a second polyimide layer 1413 is formed on the firstpolyimide layer 1412. The second polyimide layer 1413, like the firstpolyimide layer 1412, is formed by applying a polyimide solution on thefirst polyimide layer 1412, uniformly forming a film of polyimidesolution by means of a screen printing method or a spin coating method,and then curing the same. At this time, polyimide on the electrode pads1407, 1427 and 1409 are removed (FIG. 61E).

After sputtering aluminum material on the second polyimide layer 1413,the aluminum material is etched to form the wiring 1408 and dummy wiring1428 (FIG. 61F). A third polyimide layer 1414 is then formed on thesecond polyimide layer 1413. The third polyimide layer 1414 is formed todetermine the rigidity of the elastic members 1402 and protect thewiring 1408, dummy wiring 1428 and electrode pads 1407 and 1427 fromair. In this case, the thickness of the third polyimide layer 1414 isdetermined such that the wiring 1408 and dummy wiring 1428 provided onthe second polyimide layer 1413 are located within the elastic members1402 in a position where the thickness of the elastic members 1402 issubstantially halved. Following the formation of the layers, thepolyimide on the electrode pads 1409 is removed (FIG. 61G). Theelectrode pads 1409 are used for connecting the wiring to the externalpower supply. For example, in order to make the electrode pads 1409suitable for wire bonding, aluminum 1421 is further laminated bysputtering (FIG. 61H). Thereafter, the reverse side of the siliconsubstrate 1410 is subjected to anisotropic etching with use of an alkalisolution in order to form the movable plate 1401 and support member 1403(FIG. 61I).

Since the silicon nitride film 1411 lies under the first polyimide layer1412 forming the elastic members 1402, the first polyimide layer 1412 isprotected by the silicon nitride film 1411 when the silicon substrate1410 is subjected to the anisotropic etching. Following the etching, thesilicon nitride film 1411 exposed to the reverse side of the elasticmembers 1402, movable plate 1401 and support member 1403 is removed bydry etching (FIG. 61J).

Thereafter, though not shown, the first to third polyimide layers 1412,1413 and 1414 are removed from the reverse side by dry etching usingoxygen-based material, thereby forming the movable plate 1401, elasticmembers 1402 and support member 1403. An aluminum material is sputteredon the surface reflecting light, where necessary, thereby to form thereflection surface 1405 with high reflectance. Thus, the manufacture ofthe optical scanner is completed.

According to the optical scanner of the above-described embodiment, thestructure 1400 can be formed integrally by making use of semiconductorfabrication technique. Accordingly, the assembling work of respectiveparts is not needed and the very small optical scanner can bemass-produced at low cost. Moreover, the optical scanner with very highprecision in dimension and very low variance in characteristics can bemanufactured. Since polyimide or organic insulating material is used asmaterial of the elastic members 1402, the possibility of occurrence offragile-destruction is low and a large deflecting angle is obtained.Moreover, since the drive coil 1406, detection coil 1426, wiring 1408and dummy wiring 1428 are not exposed to the surface of polyimide andare formed within the elastic members 1402, degradation with the passingof time, such as oxidation due to moisture, can be prevented.

Besides, in the present embodiment, the four wiring elements 1408 aresituated at a position where the thickness of the elastic members 1402is substantially halved. In general, when the torsion-bar type opticalscanner such as the optical scanner of the present embodiment isoperated, the elastic members 1402 are greatly torsion-deformed and as aresult a stress occurs. In this case, as a matter of course, a stressacts on the wiring 1408 situated within the elastic member 1402. Thestress acting on the wiring 1408 is, for example, bending stress,tensile stress, torsional stress, etc. According to the simulationresult obtained by using the finite element method, the absolute valueof the bending or tensile stress is much greater than that of thetorsional stress. Thus, attention was paid to the tensile stress andbending stress, and the position of the wiring 40 was varied along thethickness of the elastic members 1402. The simulation results of thetensile stress and bending stress acting on the wiring 1408, which wereobtained in this case, are shown in FIGS. 62 and 63.

In the simulation, the width in cross section of each of the fouraluminum wiring elements 1408 was set at 100 μm, the thickness in crosssection of each wiring element was set at 2 μm, and the distance betweencenters of wiring elements 1408 was set at 200 μm. The wiring elements1408 are arranged symmetric with respect to a line along with the widthof the elastic member 1402 is substantially halved. In FIGS. 62 and 63,the two-division point in the thickness direction of the elastic member1402 is set at zero on the abscissa (wiring position), and a positiveregion and a negative region are set on both sides of the zero on theabscissa. The positive region corresponds to the upper side in FIG. 58,and the negative region to the lower side in FIG. 58. According to thesimulation result, as the wiring element 1408 departs from thesubstantial two-division point in the thickness direction of elasticmember 1402, the stress value of the tensile stress increases. Althoughthe rate of variation of the bending stress is not so high, the stressvalue of the bending stress increases as the wiring element departs fromthe two-division point in the thickness direction. If influences of bothstresses are considered together, the stress value is minimum at thetwo-division point in the thickness direction.

As is clear from the above, if the wiring 1408 is situated on thesurface of the elastic element 1402 as in the prior art, the wiring 1408is present at the position where the stress is high. In this case, ifthe elastic member 1402 is driven repeatedly, high stress occurs in thewiring and breakage due to fatigue may occur. By contrast, in thestructure of the present invention, the wiring 1408 is situated at theposition where the stress is minimum. Thus, the reliability of theoptical scanner can be maintained for a long time.

Moreover, in the present embodiment, the four wiring elements 1408 arearranged closely and symmetrically with respect to a central positioncorresponding to the substantial two-division point in the widthdirection of the elastic member 1402. The advantage of this arrangementwill now be described with reference to FIGS. 64 and 65. FIGS. 64 and 65show simulation results of stress values obtained when the interval ofthe wiring elements is varied in the state in which the four wiringelements 1408 are situated within the elastic member 1402. If theinterval of wiring element is increased, the wiring 1408 is arrangednear the periphery of the elastic member 1402, when the elastic member1402 is viewed from above. As is clear from the simulation result, asthe interval of wiring elements decreases, the value of bending stressdecreases. It follows from this that the reliability of wiring can bemaintained for a long time by situating the four wiring elements 1408concentratedly near the substantial two-division point in the widthdirection of the elastic member.

Like the first embodiment, in the optical scanner of this embodiment,external light is radiated on the vibrating movable plate and thereflected light can be scanned one-dimensionally. For example, thisoptical scanner can be incorporated in a laser scanning microscope shownin FIG. 66. An emission beam from a laser light source 2001 is convergedby a lens 2002 and passed through a pinhole 2003. Further, the beam ispassed through a dichroic mirror 2004 and collimated by a lens 2005. Thecollimated beam is guided to an objective lens 2008 via a X-directionalscan mirror 2006 and a Y-directional scan mirror 2007. The beam is thenconverged by the objective lens 2008 on the surface of an object 2009.The optical scanner (shown in a circle) of this embodiment is used ineach of the X-directional scan mirror 2006 and Y-directional scan mirror2007. Accordingly, if the X-directional scan mirror 2006 andY-directional scan mirror 2007 are driven in the directions of arrows,the light converged via the objective lens 2008 on the surface of object2009 can be scanned two-dimensionally. The reflected light from theobject 2009 travels in the reverse direction and passes through the lens2005. The light is then reflected by the dichroic mirror 2004, andconverged at a pinhole 2010. The light alone, which has passed throughthe pinhole 2010, reaches a photomultiplier 2011 and is detected.

In the laser scanning microscope in which the optical scanner of thisembodiment is incorporated, the X-directional scan mirror 2006 is used,for example, for high-speed scan and the Y-directional scan mirror 2007is used for low-speed scan. If these mirrors are properly selected anddriven, the surface of the object 2009 is raster-scanned. TheX-directional scan mirror 2006 needs to be driven at high speed with apredetermined scan length and thus the movable plate 1401 is normallydriven at a resonant frequency thereof.

The resonant frequency is definitively determined by the shape andmaterial of the movable plate 1401 and elastic members 1402. Strictlyspeaking, the resonant frequency is slightly influenced by themechanical characteristics of the wiring 1408 situated within theelastic member 1402. In this embodiment, the wiring 1408 is situated ata substantial two-division position in the thickness direction and inthe width direction of the elastic member 1402. Accordingly, themechanical characteristics of the wiring 1408 do not greatly influencethe resonant frequency. On the other hand, the Y-directional scan mirror2007 may be driven at a lower speed than the X-directional scan mirror2006. Thus, as long as a predetermined scan length is maintained, themovable plate 1401 may be driven at the resonant frequency or anon-resonant frequency. The movable section of the optical scanner ofthis embodiment can be more reduced in size than in the prior art, andthe high-speed observation can be easily achieved. In particular, if theoptical scanner of this embodiment is used for the mirror which needs tobe driven at high speed (the X-directional scan mirror 1006 in thisembodiment), the high-speed observation of the laser scanning microscopecan be achieved.

The present embodiment is not limited to the above-described structure,and various modifications and changes can be made. For example, thedrive coil 1406 and detection coil 1426 may be formed by plating, andnot by sputtering and etching. In particular, when a large deflectionangle is required, the number of turns of the coil needs to beincreased. If the number of turns alone is increased without increasingthe cross-sectional area of the coil, the resistance value of the coilincreases and consequently the power supply voltage and powerconsumption increase. If the coil is formed by plating, however, thethickness of the coil can be made greater than in the case of thesputtering, the aspect ratio is increased and desired specifications canbe achieved. In addition, if the aspect ratio of the drive coil 1406 isincreased, the width occupied by the drive coil 1406 can be reduced. Asa result, the detection coil 1426 can be arranged near the peripheralportion of the movable plate 1401, and the sensitivity of the detectioncoil can be increased.

In the present embodiment, the drive coil 1406 and detection coil 1426are provided individually. However, a single coil may be used for bothdriving and detection. In this case, the single coil may be selectivelyconnected to the power supply or a detection circuit by means of, e.g. achange-over switch. The coil connected to the power supply functions asa drive coil, and the coil connected to the detection circuit functionsas a detection coil.

The method of driving in this embodiment is not limited to the methodwherein the AC with the frequency equal to the resonant frequency isused to reciprocally drive the movable plate. For example, the movableplate may be driven with use of a variable method, or staticallypositioned with use of a DC.

In this embodiment, the actuator comprising the permanent magnets andcoils is used. This embodiment, however, may be modified such that anelectrostatic actuator is used. FIG. 67 is a perspective view showingthe structure of the optical scanner using the electrostatic actuator,and FIG. 68 is a sectional view taken along line A—A in FIG. 67.

In this modification, two movable electrodes 1451 and 1452 are providedon the surface of the movable plate 1401. A stationary electrode 1453 isfixed to a fixed member (not shown) so as to face the movable electrodes1451 and 1452. The movable electrodes 1451 and 1452 are electricallyconnectable to an external power supply via electrode pads 1409, wirings1408 and interlayer wiring 1454. The electrode pads 1409 and stationaryelectrode 1453 are connected to a power supply 1456 via a switch 1455.The switch 1455 is constructed so as to selectively apply a voltagebetween the stationary electrode 1453 and movable electrode 1451 orbetween the stationary electrode 1453 and movable electrode 1452. Ifvoltage is applied between the stationary electrode 1453 and movableelectrode 1451 or between the stationary electrode 1453 and movableelectrode 1452, a potential difference is provided therebetween. As aresult, an electrostatic attractive force occurs therebetween and themovable plate 1401 is driven in a predetermined direction. In thismodification, the movable electrodes 1451 and 1452 are formed on thesurface of the movable plate 1401, but the wirings 1408 are situated ata position where the thickness of the elastic members 1402 issubstantially halved. As a result, when the elastic members 1402 aredeformed, the stress acting on the wirings 1408 can be reduced and thereliability of the optical scanner maintained.

The driving method in this modification is not limited to theabove-described switching method. For example, two variable electrodesare connected to the respective movable electrodes and a predeterminedvoltage may be applied between the electrodes.

(Eleventh Embodiment)

An optical scanner according to an eleventh embodiment of the inventionwill now be described with reference to FIGS. 69-71 and 72A-72J.

FIG. 69 is a plan view showing an elastic member 1502 of the opticalscanner according to the eleventh embodiment. FIG. 70 is a sectionalview taken along line A—A in FIG. 69. FIG. 71 is a block diagram showinga control circuit for the optical scanner of the eleventh embodiment,and FIGS. 72A to 72J show manufacturing steps of the optical scanner ofthe eleventh embodiment.

In addition to the structure of the optical scanner according to the10th embodiment, the optical scanner of this embodiment incorporatesstrain gages. By detecting the amount of strain, the vibration of themovable plate can be monitored. Moreover, the optical scanner of thisembodiment includes a self-stimulus oscillation circuit for constantlyvibrating the movable plate with a reflection surface at a resonantfrequency. In the other respects of the structure, the optical scannerof this embodiment is common to that of the tenth embodiment. Thus, thecommon structural elements are denoted by like reference numerals and adescription thereof is omitted.

FIG. 69 shows wiring 1508 disposed within the elastic member 1502, forthe purpose of convenience.

The optical scanner of this embodiment has a torsion bar type structure,like the tenth embodiment. Two wiring elements 1508 connected to a drivecoil 1506 (see FIG. 72D) are disposed within the elastic member 1502 ata position where the thickness of the elastic member is substantiallyhalved, as in the tenth embodiment. The two wiring elements 1508 arearranged concentrated and symmetric with respect to the position wherethe elastic member is substantially divided into two in its widthdirection. In the tenth embodiment the vibration detection coil isprovided on the movable plate, whereas in this embodiment such avibration detection coil is not provided. Four strain gages 1530,instead of the vibration detection coil, are provided at four corners ofthe elastic member 1502. Each strain gage 1530 is constructed to measurethe amount of strain of the elastic member 1502. The strain gage 1530is, in general, formed by doping phosphorus in polysilicon or by using athin film of platinum or titanium. In any of these methods, asemiconductor 5 process can be utilized to form the strain gage in athin film shape. Four wiring elements 1531 extend from the four straingages 1530. The two wiring elements 1531 extending from the two straingages 1530 formed at the boundary between the movable plate 1501 andelastic member 1502 pass through the inside of the elastic member 1502and reach a support member 1503. Outputs from the stain gages 1530 aresupplied to a bridge circuit (not shown) provided on the support member1503 or outside the optical scanner via the wiring 1531, and a variationin resistance due to strain is detected.

In the ninth and tenth embodiments, the description was given of theadvantage of situating the wiring at the location where the stresswithin the elastic member is lowest. In the present embodiment, however,it is desirable that the strain gages be situated at the locations wherethe strain is highest, that is, the stress is greatest, in order toincrease the detection sensitivity of the strain gages as high aspossible. In this case, since the stress increases toward the peripheryof the elastic member in the thickness and width directions of theelastic member, the strain gages should preferably be situated near theperiphery of the elastic member.

Accordingly, in this embodiment, as shown in FIG. 69, the strain gages1530 are arranged nearly at four corners of the rectangular elasticmember 1502. If attention is paid to the absolute value of stress, it isideal that the strain gages 1530 are exposed to the surface of theelastic member 1502 in its thickness direction. If the strain gages 1530are exposed to air, however, the gages 1530 may possibly degrade withthe passing of time. It is thus considered optimal that the strain gagesare situated within the elastic member 1502 and near the periphery ofthe elastic member 1502.

As is shown in FIG. 70, the strain gages 1530 are situated within theelastic member 1502 and near the lower part of the elastic member 1502in its thickness direction. On the other hand, the wiring 1531, like thewiring 1508 (see FIG. 69) connected to the drive coil, is situated atthe substantial two-division point in the thickness direction of theelastic member 1502.

The strain gages 1530 and wiring 1531 are connected by interlayer wiring1532.

The operation of the optical scanner of this embodiment will now bedescribed.

If current is supplied to the drive coil 1506 and the movable plate 1501is displaced, the amount of strain of the elastic member 1502 ismeasured by the strain gages 1530. At this time, outputs from the straingages 1530 are amplified by a strain detection circuit 1551, as shown inFIG. 71. An output from the strain detection circuit 1551 is an AC. Ifan input waveform is a sine waveform, an output of the strain detectioncircuit 1551 is also a sine wave. An output signal from the strainamount is input to a BPF (Band Pass Filter) 1552, and a noise signal,other than a signal near a resonant frequency, is removed. The phase ofthe signal from the BPF 1552 is adjusted by a phase device 1553. Whilethe optical scanner vibrates at a resonant frequency, the phase devicecorrects a phase error between the input waveform and the outputwaveform and delivers the corrected signal to an amplifier 1554. Theamplifier 1554 serves also as a power supply. The amplifier 1554determines a maximum voltage value and thus keeps the deflection angleof the movable plate 1501 constant at the time of resonance. The straindetection circuit 1551, phase device 1553 and amplifier 1554 constitutethe self-stimulus oscillation circuit. With this structure, the movableplate 1501 is always driven and controlled at the resonant frequency.

FIGS. 72A to 72J illustrate a method of manufacturing the opticalscanner of this embodiment. This method is basically the same as themethod in the tenth embodiment. Different steps alone will be describedbelow.

After a first polyimide layer 1512 is formed, aluminum material ispatterned to form the drive coil 1506 and electrode pads 1507 and 1509.Before a second polyimide layer 1513 is formed, strain gages 1530 areformed at predetermined positions (preferably near four corners of theelastic member) (FIGS. 72A-72D). The materials used in the respectivesteps are the same as described in the preceding embodiments. In thisstep, it is desirable to thin as much as possible the first polyimidelayer 1512 to such a degree that the reliability of each electricelement disposed within the optical scanner can be maintained, in orderto situate the strain gages 1530 at positions with high stress. In thiscase, the electric elements such as coil 1506 are formed at the sameposition in the thickness direction. Since each electric element isformed at a portion with high rigidity (i.e. the portion constitutingthe movable plate 1501 or support member 1503), the stress acting on theelectric element can be ignored. In the left part of the elastic member1502 in FIG. 72D, dummy gages 1540 are formed to substantially equalizethe characteristics of the right and left parts of the elastic member1502. Moreover, the same electric elements as those formed within theright part of the elastic member 1502 are formed within the left part ofthe elastic member 1502 for the same reason. A description of this stepis omitted.

After the second polyimide layer 1513 is formed, the portions on theelectrode pads 1507 and 1509 and strain gages 1530 are patterned (FIG.72E). Interlayer wirings 1532 and 1542 are formed at the patternedportions. Wiring 1508 connected to the drive coil 1506 and wirings 1531and 1541 connected to the strain gages 1530 and dummy gages 1540 areformed on the interlayer wirings 1532 and 1542 (FIG. 72F). In this case,it is desirable to situate the wirings 1531 and 1541 at the substantialtwo-division point in the thickness direction of the elastic member1502. The other steps are the same as those in the tenth embodiment.

According to the optical scanner of this embodiment, the strain gages1530 are disposed within the elastic member 1502 to directly measure theamount of strain of the elastic member 1502. Thereby the deflectionangle of the movable plate 1501 can be directly found. Since the straingages 1530 can be formed monolithically with the optical scanner body byusing the semiconductor process, the strain gages 1530 can be integratedwithout great change in manufacturing steps.

According to this embodiment, the electric elements such as wirings 1508and 1531 are situated within the elastic member 1502 and thus thereliability of the optical scanner can be maintained for a long time.Since these wirings are situated in a concentrated manner near aposition where the thickness of the elastic member is substantiallyhalved and also the width thereof is substantially halved, the stressacting on the wirings can be reduced. As a result, breakage of wires canbe remarkably prevented. At the same time, in order to increase as highas possible the sensitivity of the strain gages or detection elements,the strain gages are situated at positions with high stress both in thethickness and width directions of the elastic member. Therefore, thescanner characteristics can be optimized.

Like the tenth embodiment, the scanner of this embodiment can be appliedto a laser scanning microscope.

In the present embodiment, the elastic member 1502 is described asmainly performing torsional vibration.

However, as in the ninth embodiment, the elastic member 1502 may beadapted to mainly perform bending vibration.

In the case of bending vibration, the arrangement in the width directionof the elastic member is not so important. Only by optimizing thearrangement in the thickness direction, can the characteristics of theoptical scanner be optimized.

In the present embodiment, the strain resistance effect is utilized tomeasure the deformation amount of the elastic member. However, avariation in resistance value due to a variation in volume of theresistor may be utilized. Needless to say, such various modifications aswere described in connection with the ninth and tenth embodiments can bemade.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. An optical scanner comprising: a support memberfor fixation on a given member; a movable plate provided with areflection surface for reflecting light; an elastic member coupling themovable plate and the support member, the elastic member comprising aplurality of laminated organic elastic insulating layers; and anelectric element comprising (i) an actuator, provided on the movableplate, for making a driving force act between the movable plate and thesupport member, and (ii) wiring for use in supplying an electric signalto the actuator, the electric element being designed to supply apredetermined signal to the actuator through the wiring so that theelastic member is elastically deformed to deflect the movable plate, tothereby produce the driving force, the electric element being providedbetween the organic elastic insulating layers in the elastic member. 2.The optical scanner according to claim 1, further comprising anotherelastic member identical to the elastic member, and wherein the twoelastic members are provided to connect both sides of the movable plateto the support member.
 3. The optical scanner according to claim 2,wherein one of the elastic members is provided with the electric elementfor supplying the electric signal to the actuator, and the other isprovided with a dummy electric element.
 4. The optical scanner accordingto one of claims 1 and 2, wherein said electric element is provided in aposition where the thickness of the elastic member in the direction ofthe lamination is substantially halved.
 5. The optical scanner accordingto one of claims 1 and 2, wherein said electric element is provided in aposition where the width of the elastic member is substantially halved,and the width direction of the elastic member is perpendicular to thethickness direction of the elastic member and to a direction of a lineextending from the support member to the movable plate.
 6. The opticalscanner according to one of claims 1 and 2, wherein one of the elasticmember and the movable plate is provided with detection means fordetecting displacement of the movable plate, and the electric elementincludes wiring of the detection means.
 7. The optical scanner accordingto claim 6, wherein said detection means includes a resistor capable ofdetecting a deflection angle of the movable plate on the basis of thestate of deformation of the elastic member, and wherein the resistor isprovided at the elastic member.
 8. The optical scanner according toclaim 7, wherein the resistor comprises a piezoresistor.
 9. The opticalscanner according to claim 7, wherein said detection means is providedwithin the elastic member and near a peripheral portion of the elasticmember in the thickness direction and the width direction of the elasticmember.
 10. The optical scanner according to claim 6, further comprisingat least one magnet, and wherein said detection means comprises a coilwhich is moved in a magnetic field produced by the magnet to produce anelectromotive force, and the coil is provided at the movable plate. 11.The optical scanner according to claim 6, further comprising controlmeans for controlling the electric signal supplied to the actuator onthe basis of an output from the detection means, thereby driving themovable plate at a resonant frequency.
 12. The optical scanner accordingto one of claims 1 and 2, wherein said support member, said movableplate, said elastic member and said electric element are monolithicallyformed as one body by a semiconductor fabrication process.
 13. Theoptical scanner according to one of claims 1 and 2, wherein: theactuator includes a part of a driving coil; and the optical scannercomprises an electromagnetic actuating type optical scanner.
 14. Theoptical scanner according to claim 13, wherein the driving coil isformed in such a manner as to extend through the movable plate, theelastic member and the support member.
 15. The optical scanner accordingto claim 13, wherein the driving coil is formed in such a manner as toextend through the movable plate only.
 16. The optical scanner accordingto claim 13, wherein a pitch of those parts of said driving coil whichfunction as the actuator is set at a smaller value than that of theother parts of said driving coil, and a width of those parts of saiddriving coil which function as the actuator is set at a smaller valuethan that of other parts of said driving coil.
 17. The optical scanneraccording to one of claims 1 and 2, wherein the actuator includes atleast one electrode, and the optical scanner comprises an electrostaticactuating type optical scanner.
 18. The optical scanner according toclaim 1, wherein: the movable plate has an end supported by the elasticmember; and the elastic member performs bending vibrations with thedriving force.
 19. The optical scanner according to claim 1, wherein:the movable plate has an end supported by the elastic member; and theelastic member performs bending vibrations and torsion vibrations withthe driving force.
 20. An optical scanner comprising: a support memberfor fixing the scanner to a given member; a movable plate having atleast one surface serving as a reflecting surface for reflecting light;an elastic member for connecting said support member to said movableplate, said elastic member including a plurality of laminated elasticinsulating layers, and an electric element comprising (i) an actuator,provided at least on the movable plate, for making a driving force actbetween the movable plate and the support member, and (ii) wiring foruse in supplying an electric signal to the actuator, the electricelement being designed to supply a predetermined signal to the actuatorthrough the wiring so that the elastic member is elastically deformed todeflect the movable plate, to thereby produce the driving force, whereinthe electric element is provided between the laminated/elasticinsulating layers so that the electric element is covered by thelaminated elastic insulating layers.